Revenue from Contracts with Customers
We provide drilling services on a day rate contract basis. Under day rate contracts, we provide an integrated service that includes the provision of a drilling rig and rig crews for which we receive a daily rate that may vary between the full rate and zero rate throughout the duration of the contractual term, depending on the operations of the rig. We also may receive lump-sum fees or similar compensation for the mobilization, demobilization and capital upgrades of our rigs. Our customers bear substantially all of the costs of constructing the well and supporting drilling operations, as well as the economic risk relative to the success of the well.
Our integrated drilling service provided under each drilling contract is a single performance obligation satisfied over time and comprised of a series of distinct time increments, or service periods. Total revenue is determined for each individual drilling contract by estimating both fixed and variable consideration expected to be earned over the contract term. Fixed consideration generally relates to activities such as mobilization, demobilization and capital upgrades of our rigs that are not distinct within the context of our contracts and is recognized on a straight-line basis over the contract term. Variable consideration generally relates to distinct service periods during the contract term and is recognized in the period when the services are performed.
The amount estimated for variable consideration is only recognized as revenue to the extent that it is probable that a significant reversal will not occur during the contract term. We have applied the optional exemption afforded in Update 2014-09 and have not disclosed the variable consideration related to our estimated future day rate revenues. The remaining duration of our drilling contracts based on those in place as of March 31, 2018 was between approximately one month and five years.
Day Rate Drilling Revenue
Our drilling contracts provide for payment on a day rate basis and include a rate schedule with higher rates for periods when the drilling unit is operating and lower rates or zero rates for periods when drilling operations are interrupted or restricted. The day rate invoiced to the customer is determined based on the varying rates applicable to specific activities performed on an hourly basis. Day rate consideration is allocated to the distinct hourly increment to which it relates within the contract term and is generally recognized consistent with the contractual rate invoiced for the services provided during the respective period. Invoices are typically billed to our customers on a monthly basis and payment terms on customer invoices typically range 30 - 45 days.
Certain of our contracts contain performance incentives whereby we may earn a bonus based on pre-established performance criteria. Such incentives are generally based on our performance over individual monthly time periods or individual wells. Consideration related to performance bonus is generally recognized in the specific time period to which the performance criteria was attributed.
We may receive termination fees if certain drilling contracts are terminated by the customer prior to the end of the contractual term. Such compensation is recognized as revenues whereby our performance obligation is satisfied, the termination fee can be reasonably measured and collection is probable.
Mobilization / Demobilization Revenue
In connection with certain contracts, we receive lump-sum fees or similar compensation for the mobilization of equipment and personnel prior to the commencement of drilling services or the demobilization of equipment and personnel upon contract completion. Fees received for the mobilization or demobilization of equipment and personnel are included in operating revenues. The costs incurred in connection with the mobilization and demobilization of equipment and personnel are included in contract drilling expense.
Mobilization fees received prior to commencement of drilling operations are recorded as a contract liability and amortized on a straight-line basis over the contract term. Demobilization fees expected to be received upon contract completion are estimated at contract inception and recognized on a straight-line basis over the contract term. In some cases, demobilization fees may be contingent upon the occurrence or non-occurrence of a future event. In such cases, this may result in cumulative-effect adjustments to demobilization revenues upon changes in our estimates of future events during the contract term.
Capital Upgrade / Contract Preparation Revenue
In connection with certain contracts, we receive lump-sum fees or similar compensation for requested capital upgrades to our drilling rigs or for other contract preparation work. Fees received are recorded as a contract liability and amortized on a straight-line basis over the contract term to operating revenues. Costs incurred for capital upgrades are capitalized and depreciated over the useful life of the asset.
Contract Assets and Liabilities
Contract assets and liabilities are presented net on our condensed consolidated balance sheet on a contract-by-contract basis. Current contract assets and liabilities are included in other current assets and accrued liabilities and other, respectively, and noncurrent contract assets and liabilities are included in other assets, net, and other liabilities, respectively, on our condensed consolidated balance sheets.
Contract assets represent amounts previously recognized as revenue but for which the right to invoice the customer is dependent upon our future performance. Once the previously recognized revenue is invoiced, the corresponding contract asset, or a portion thereof, is transferred to accounts receivable. Contract liabilities generally represent fees received for mobilization or capital upgrades.
The following table summarizes our trade receivables, contract assets and contract liabilities (in millions):
March 31, 2018
December 31, 2017
Current contract assets
Noncurrent contract assets
Current contract liabilities (deferred revenue)
Noncurrent contract liabilities (deferred revenue)
Significant changes in contract assets and liabilities during the period are as follows (in millions):
Balance as of December 31, 2017
Increase due to cash received
Decrease due to amortization of deferred revenue that was included in the beginning contract liability balance
Decrease due to amortization of deferred revenue that was added during the period
Decrease due to transfer to receivables during the period
Balance as of March 31, 2018
Deferred Contract Costs
Costs incurred for upfront rig mobilizations and certain contract preparation are attributable to our future performance obligation under each respective drilling contract. Such costs are deferred and amortized on a straight-line basis over the contract term. Demobilization costs are recognized as incurred upon contract completion. Costs associated with the mobilization of equipment and personnel to more promising market areas without contracts are expensed as incurred. Deferred contract costs were included in other current assets and other assets, net, on our condensed consolidated balance sheets and totaled $44.5 million and $40.6 million as of March 31, 2018 and December 31, 2017, respectively. During the three months ended March 31, 2018 and 2017, amortization of such costs totaled $6.8 million and $6.6 million, respectively.
Deferred Certification Costs
We must obtain certifications from various regulatory bodies in order to operate our drilling rigs and must maintain such certifications through periodic inspections and surveys. The costs incurred in connection with maintaining such certifications, including inspections, tests, surveys and drydock, as well as remedial structural work and other compliance costs, are deferred and amortized on a straight-line basis over the corresponding certification periods. Deferred regulatory certification and compliance costs were included in other current assets and other assets, net, on our condensed consolidated balance sheets and totaled $14.6 million and $15.3 million as of March 31, 2018 and December 31, 2017, respectively. During the three months ended March 31, 2018 and 2017, amortization of such costs totaled $3.1 million and $3.1 million, respectively.
Future Amortization of Contract Liabilities and Deferred Costs
Our contract liabilities and deferred costs are amortized on a straight-line basis over the contract term or corresponding certification period to operating revenues and contract drilling expense, respectively. Expected future amortization of our contract liabilities and deferred costs recorded as of March 31, 2018 is set forth in the table below (in millions):
2021 and Thereafter
Amortization of contract liabilities
Amortization of deferred costs