Goodwill and Acquired Intangible Assets - Gross Carrying Amount and Accumulated Amortization of Intangible Asset (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finite-lived Intangible Assets [Roll Forward]
Beginning of year	$ 18,305	$ 24,807	$ 18,937
Acquired CDI, including measurement period adjustments	2,129	(676)	10,170
Amortization expense	(5,857)	(5,826)	(4,300)
End of year	$ 14,577	$ 18,305	$ 24,807
Remaining average amortization period for CDI	44 months	47 months	58 months