Income Taxes - Components of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Current	$ 4,152	$ 3,813	$ 26,359
Deferred	(2,958)	(84,585)	4,108
Total income tax expense (benefit)	$ 1,194	$ (80,772)	$ 30,467