Income Taxes - Uncertain tax positions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
A reconciliation of the beginning and ending liability for uncertain tax positions
Balance at beginning of year	$ 490	$ 464
Increase Resulting from Current Period Tax Positions	73	26
Increases for tax position taken in prior years	1,809
Decreases due to settlements with taxing authorities	(11)
Balance at the end of year	2,361	490
Unrecognized tax benefits that would affect the effective tax rate, if recognized	438
Accrued interest and penalties reported as income tax liability	$ 79	$ 110