Income Taxes - Uncertain Tax Positions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Uncertain Tax Positions
Balance at beginning of year	$ 2,983	$ 2,141	$ 1,101
Increases for prior positions	7	70	97
Increases for current year positions	724	775	943
Other increases	0	0	0
Decreases due to settlements	0	0	0
Expiration of the statute of limitations for the assessment of taxes	0	0	0
Other decreases	(2)	(3)	0
Balance at end of year	$ 3,712	$ 2,983	$ 2,141