Income Taxes - Allocation of Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income tax (benefit) expense	$ (17,881)	$ 7,147	$ 808
Income tax recorded in accumulated other comprehensive (loss) income	(2,488)	2,003	(300)
Total income tax (benefit) expense	$ (20,369)	$ 9,150	$ 508