Income Taxes - Current and Deferred (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
U.S. federal	$ (160,761)	$ (19,937)	$ 5,088
State	(810)	2,871	8,227
Current Income Tax Expense (Benefit), Total	(102,080)	14,780	89,865
Deferred:
State	(3,226)	(22,673)	(7,142)
Deferred Income Tax Expense (Benefit), Total	19,110	(201,611)	(187,903)
Total income tax expense (benefit)	(82,970)	(186,831)	(98,038)
United States
Deferred:
U.S. federal	49,020	(164,297)	(182,518)
Outside the U.S
Current:
Outside the U.S.	59,491	31,846	76,550
Deferred:
Outside the U.S.	$ (26,684)	$ (14,641)	$ 1,757