Income Taxes - Uncertain Tax Positions Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at January 1	$ 257	$ 665	$ 419
Additions (reductions) for tax positions of prior years	(3)	(399)
Additions (reductions) for tax positions of prior years			477
Additions (reductions) for tax positions of current year	0
Reductions for settlements with tax authorities		0	0
Reductions for lapse of statute of limitations	(31)	(9)	(231)
Balance at December 31	$ 223	$ 257	$ 665