Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance			$ 605,224	$ 321,673
Other comprehensive income (loss)	$ 22	$ 48	(178)	184
Ending Balance	659,225	600,674	659,225	600,674
Unrealized Net Gains and (Losses) on Securities Available-for-Sale
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance			(612)	(224)
Other comprehensive income (loss), before reclassifications			(168)	172
Amounts reclassified from accumulated other comprehensive income (loss), net of tax of ($61) (1)			178
Other comprehensive income (loss)			10	172
Ending Balance	(602)	(52)	(602)	(52)
Other comprehensive income (loss), before reclassifications, tax			68	(115)
Reclassification from AOCI, tax			(61)
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance			12	0
Other comprehensive income (loss), before reclassifications			(10)	12
Amounts reclassified from accumulated other comprehensive income (loss), net of tax of ($61) (1)			0
Other comprehensive income (loss)			(10)	12
Ending Balance	$ 2	$ 12	2	$ 12
Other comprehensive income (loss), before reclassifications, tax			$ 4