Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Unrecognized tax benefits [Roll Forward]
Balance at January 1,	$ 18,461	$ 29,160
Additions for tax positions related to the current year	80	184
Reductions for the Impact of the Tax Act	0	(10,859)
Reductions for tax positions related to prior years	(34)	(24)
Balance at December 31,	$ 18,507	$ 18,461