Income Taxes	6 Months Ended
Jun. 30, 2018
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract]
Income Taxes	Income Taxes Historically, we have calculated our provision for income taxes during interim reporting periods by applying the estimated annual effective tax rate for the full fiscal year to pre-tax income or loss, excluding discrete items, for the reporting period. We determined that since small changes in estimated pre-tax income or loss would result in significant changes in the estimated annual effective tax rate, the historical method would not provide a reliable estimate of income taxes for the three-month and six-month periods ended June 30, 2018 and 2017. We used a discrete effective tax rate method to calculate income taxes for the three-month and six-month periods ended June 30, 2018. We will continue to evaluate income tax estimates under the historical method in subsequent quarters and employ a discrete effective tax rate method if warranted. Discrete income tax benefit for the three-month period ended June 30, 2018 was $2.3 million and was primarily attributable to U.S. tax reform, partially offset by discrete tax expense related to rig sales and unrecognized tax benefits associated with tax positions taken in prior years. Discrete income tax benefit for the six-month period ended June 30, 2018 was $11.2 million and was primarily attributable to U.S. tax reform and a restructuring transaction, partially offset by discrete tax expense related to repurchase and redemption of senior notes, the effective settlement of liabilities for unrecognized tax benefits associated with tax positions taken in prior years and rig sales. Discrete income tax expense for the three-month period ended June 30, 2017 was $2.2 million and was primarily attributable to the debt exchange and repurchases we undertook during the first quarter of 2017 and a settlement of a previously disclosed legal contingency. Discrete income tax expense for the six-month period ended June 30, 2017 was $9.8 million and was primarily attributable to the exchange offers and debt repurchases, a restructuring transaction, the effective settlement of a liability for unrecognized tax benefits associated with a tax position taken in prior years and a settlement of a previously disclosed legal contingency. U.S Tax Reform The U.S. Tax Cuts and Jobs Act (“U.S. tax reform”) was enacted on December 22, 2017 and introduced significant changes to U.S. income tax law, including a reduction in the statutory income tax rate from 35% to 21% effective January 1, 2018, a one-time transition tax on deemed repatriation of deferred foreign income, a base erosion anti-abuse tax that effectively imposes a minimum tax on certain payments to non-U.S. affiliates, new and revised rules relating to the current taxation of certain income of foreign subsidiaries and revised rules associated with limitations on the deduction of interest. Due to the timing of the enactment of U.S. tax reform and the complexity involved in applying its provisions, we made reasonable estimates of its effects and recorded such amounts in our consolidated financial statements as of December 31, 2017 on a provisional basis. As we continue to analyze applicable information and data, and interpret any additional guidance issued by the U.S. Treasury Department, the Internal Revenue Service and others, we may make adjustments to the provisional amounts throughout the one-year measurement period as provided by Staff Accounting Bulletin No. 118. Our accounting for the enactment of U.S. tax reform will be completed during 2018, and any adjustments we recognize could be material. The ongoing impact of U.S. tax reform may result in an increase in our consolidated effective income tax rate in future periods. During the three-month and six-month periods ended June 30, 2018, we recognized a tax benefit of $7.1 million and $11.7 million, respectively, associated with the one-time transition tax on deemed repatriation of the deferred foreign income of our U.S. subsidiaries.

Income Taxes

Historically, we have calculated our provision for income taxes during interim reporting periods by applying the estimated annual effective tax rate for the full fiscal year to pre-tax income or loss, excluding discrete items, for the reporting period. We determined that since small changes in estimated pre-tax income or loss would result in significant changes in the estimated annual effective tax rate, the historical method would not provide a reliable estimate of income taxes for the three-month and six-month periods ended June 30, 2018 and 2017. We used a discrete effective tax rate method to calculate income taxes for the three-month and six-month periods ended June 30, 2018. We will continue to evaluate income tax estimates under the historical method in subsequent quarters and employ a discrete effective tax rate method if warranted.

Discrete income tax benefit for the three-month period ended June 30, 2018 was $2.3 million and was primarily attributable to U.S. tax reform, partially offset by discrete tax expense related to rig sales and unrecognized tax benefits associated with tax positions taken in prior years. Discrete income tax benefit for the six-month period ended June 30, 2018 was $11.2 million and was primarily attributable to U.S. tax reform and a restructuring transaction, partially offset by discrete tax expense related to repurchase and redemption of senior notes, the effective settlement of liabilities for unrecognized tax benefits associated with tax positions taken in prior years and rig sales.

Discrete income tax expense for the three-month period ended June 30, 2017 was $2.2 million and was primarily attributable to the debt exchange and repurchases we undertook during the first quarter of 2017 and a settlement of a previously disclosed legal contingency. Discrete income tax expense for the six-month period ended June 30, 2017 was $9.8 million and was primarily attributable to the exchange offers and debt repurchases, a restructuring transaction, the effective settlement of a liability for unrecognized tax benefits associated with a tax position taken in prior years and a settlement of a previously disclosed legal contingency.

U.S Tax Reform

The U.S. Tax Cuts and Jobs Act (“U.S. tax reform”) was enacted on December 22, 2017 and introduced significant changes to U.S. income tax law, including a reduction in the statutory income tax rate from 35% to 21% effective January 1, 2018, a one-time transition tax on deemed repatriation of deferred foreign income, a base erosion anti-abuse tax that effectively imposes a minimum tax on certain payments to non-U.S. affiliates, new and revised rules relating to the current taxation of certain income of foreign subsidiaries and revised rules associated with limitations on the deduction of interest.

Due to the timing of the enactment of U.S. tax reform and the complexity involved in applying its provisions, we made reasonable estimates of its effects and recorded such amounts in our consolidated financial statements as of December 31, 2017 on a provisional basis. As we continue to analyze applicable information and data, and interpret any additional guidance issued by the U.S. Treasury Department, the Internal Revenue Service and others, we may make adjustments to the provisional amounts throughout the one-year measurement period as provided by Staff Accounting Bulletin No. 118. Our accounting for the enactment of U.S. tax reform will be completed during 2018, and any adjustments we recognize could be material. The ongoing impact of U.S. tax reform may result in an increase in our consolidated effective income tax rate in future periods.

During the three-month and six-month periods ended June 30, 2018, we recognized a tax benefit of $7.1 million and $11.7 million, respectively, associated with the one-time transition tax on deemed repatriation of the deferred foreign income of our U.S. subsidiaries.