Unaudited Condensed Consolidated Financial Statements (Policies)	9 Months Ended
	Sep. 30, 2019
Unaudited Condensed Consolidated Financial Statements [Abstract]
New Accounting Pronouncements	New Accounting Pronouncements Recently adopted accounting standards Derivatives and Hedging - In August 2017, the Financial Accounting Standards Board (the "FASB") issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities ("Update 2017-12"), which makes more hedging strategies eligible for hedge accounting, amends presentation and disclosure requirements and changes how companies assess effectiveness, including the elimination of separate measurement and recognition of ineffectiveness on designated hedging instruments. This update is effective for annual and interim periods beginning after December 15, 2018, with early adoption permitted. We adopted Update 2017-12 effective January 1, 2019. As a result, beginning on the effective date, we will no longer separately measure and recognize ineffectiveness on our designated cash flow hedges. Update 2017-02 requires a modified retrospective adoption approach whereby amounts previously recorded to earnings for hedge ineffectiveness on hedging relationships that exist as of the adoption date are recorded as a cumulative effect adjustment to opening retained earnings. As of our adoption date, we had no amounts previously recorded for ineffectiveness for hedging relationships that existed as of our adoption date and therefore no cumulative effect adjustment to retained earnings was recorded. Leases - During 2016, the FASB issued Update 2016-02, Leases (Topic 842) ("Update 2016-02"), which requires an entity to recognize lease assets and lease liabilities on the balance sheet and to disclose key qualitative and quantitative information about the entity's leasing arrangements. This update is effective for annual and interim periods beginning after December 15, 2018, with early adoption permitted. During our evaluation of Update 2016-02, we concluded that our drilling contracts contain a lease component. In July 2018, the FASB issued Accounting Standard Update 2018-11, Leases (Topic 842), Targeted Improvements, which (1) provided for a new transition method whereby entities could elect to adopt the Update using a prospective with cumulative catch-up approach (the "effective date method") and (2) provided lessors with a practical expedient, by class of underlying asset, to not separate lease and non-lease components and account for the combined component under Topic 606 when the non-lease component is the predominant element of the combined component. The lessor practical expedient is limited to circumstances in which the lease, if accounted for separately, would be classified as an operating lease under Topic 842. We adopted Update 2016-02, effective January 1, 2019, using the effective date method. With respect to our drilling contracts, which contain a lease component, we elected to apply the practical expedient to not separate the lease and non-lease components and account for the combined component under Topic 606. With respect to all of our drilling contracts that existed on the adoption date, we concluded that the criteria to elect the lessor practical expedient had been met. As a result, we will continue to recognize the revenue associated with our drilling contracts under Topic 606. Therefore, we do not expect any change in our revenue recognition patterns or disclosures as a result of our adoption of Topic 842. With respect to leases whereby we are the lessee, we elected several practical expedients afforded under Topic 842. We elected the package of practical expedients permitted under the transition guidance of Topic 842, including the hindsight practical expedient which permits entities to use hindsight in determining the lease term and assessing impairment. We also elected the practical expedient to not separate lease components from non-lease components for all asset classes, with the exception of office space. Furthermore, we also elected the practical expedient that permits entities not to apply the recognition requirements for leases with a term of 12 months or less. Upon adoption of Update 2016-02 on January 1, 2019, we recognized lease liabilities and right-of-use assets of $64.6 million and $53.7 million, respectively. See Note 14 for additional information. Recently issued accounting standards Defined Benefit Plans - In August 2018, the FASB issued ASU No. 2018-14, Compensation – Retirement Benefits – Defined Benefit Plans – General (Subtopic 715-20): Disclosure Framework – Changes to the Disclosure Requirements for Defined Benefit Plans, which modifies the disclosure requirements for employers that sponsor defined benefit pension or other post-retirement plans. We will be required to adopt the amended guidance in annual and interim reports beginning January 1, 2021, with early adoption permitted. Adoption is required to be applied on a retrospective basis to all periods presented. We are in the process of evaluating the impact this amendment will have on our condensed consolidated financial statements. Credit Losses - In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments ("Update 2016-13"), which requires companies to measure credit losses of financial instruments, including customer accounts receivable, utilizing a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. Update 2016-13 is effective for fiscal years beginning after December 15, 2019, with early adoption permitted. We are currently in the process of evaluating the impact this amendment will have on our condensed consolidated financial statements.