Income Taxes Income Taxes - Allocation of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Continuing operations	$ 323,859	$ 431,761	$ 207,510
Discontinued operations	(364,856)	24,052	88,216
Income tax (benefit) expense from continuing and discontinued operations	$ (40,997)	$ 455,813	$ 295,726