Income Taxes - Components of Income Tax Expense (Benefit) from Continuing Operations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Current U.S. federal									$ 94,873	$ 273,205	$ 138,871
Current State and local									18,810	35,057	16,677
Current Sub-total									113,683	308,262	155,548
Deferred U.S. federal									(381,063)	32,783	(110,390)
Deferred State and local									(33,993)	6,157	(19,240)
Deferred Sub-total									(415,056)	38,940	(129,630)
Income tax (benefit) expense from continuing operations	$ (219,767)	$ (20,087)	$ (9,905)	$ (51,614)	$ 43,280	$ 73,871	$ 214,856	$ 15,195	$ (301,373)	$ 347,202	$ 25,918