Goodwill and Acquired Intangible Assets - Gross Carrying Amount and Accumulated Amortization of Intangible Asset (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Beginning of year	$ 8,594	$ 7,454	$ 718
Acquired CDI	8,464	2,564	7,769
Amortization expense	(2,486)	(1,424)	(1,033)
End of year	$ 14,572	$ 8,594	$ 7,454
Remaining Average Amoritzation Period	64 months	67 months	71 months