Income Taxes	6 Months Ended
Jun. 30, 2017
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract]
Income Taxes	Income Taxes We have historically 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 our estimated annual effective tax rate, the historical method utilized would not provide a reliable estimate of income taxes for the three-month and six-month periods ended June 30, 2017. We used a discrete effective tax rate method to calculate income taxes for the three-month and six-month periods ended June 30, 2017. 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 expense for the three-month and six-month periods ended June 30, 2017 was $2.2 million and $9.8 million, respectively, 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. Discrete income tax expense of $2.0 million and $5.4 million for the three-month and six-month periods ended June 30, 2016, respectively, resulted primarily from the gain on debt extinguishment, income from the ENSCO DS-9 lump-sum consideration and restructuring transactions involving certain of our subsidiaries.

Income Taxes

We have historically 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 our estimated annual effective tax rate, the historical method utilized would not provide a reliable estimate of income taxes for the three-month and six-month periods ended June 30, 2017. We used a discrete effective tax rate method to calculate income taxes for the three-month and six-month periods ended June 30, 2017. 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 expense for the three-month and six-month periods ended June 30, 2017 was $2.2 million and $9.8 million, respectively, 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. Discrete income tax expense of $2.0 million and $5.4 million for the three-month and six-month periods ended June 30, 2016, respectively, resulted primarily from the gain on debt extinguishment, income from the ENSCO DS-9 lump-sum consideration and restructuring transactions involving certain of our subsidiaries.