Income Taxes - Allocation of Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes
Income tax (benefit) expense	$ (736)	$ (17,881)	$ 7,147
Income tax recorded in accumulated other comprehensive (loss) income	685	(2,488)	2,003
Total income tax (benefit) expense	$ (51)	$ (20,369)	$ 9,150