Income Taxes - Components of the Provision for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal					$ (2,178)	$ (68,601)	$ 60,079
State and local					410	515	6,322
Foreign					4,692	2,742	2,034
Total current expense (benefit)					2,924	(65,344)	68,435
Deferred:
Federal					42,246	(9,349)	81,682
State and local					4,057	8,857	3,657
Total deferred expense (benefit)					46,303	(492)	85,339
Total income tax expense (benefit)	$ (165,231)	$ 34,506	$ 45,391	$ 19,498	$ 49,227	$ (65,836)	$ 153,774