Acquisition of First Priority Financial Corp. (Pro Forma Information) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Net interest income after loan loss provision	$ 26,289	$ 20,308	$ 20,296	$ 17,115	$ 17,070	$ 17,202	$ 17,305	$ 17,181	$ 84,008	$ 68,758	$ 55,434
Noninterest income	6,050	5,302	3,622	2,934	4,695	3,003	2,874	2,049	17,908	12,621	7,462
Noninterest expense	$ 21,419	$ 18,174	$ 15,403	$ 15,581	$ 16,171	$ 14,683	$ 14,796	$ 14,303	$ 70,577	$ 59,953	50,171
First Priority Financial Corp. [Member]
Business Acquisition [Line Items]
Net interest income after loan loss provision											66,370	$ 55,082
Noninterest income											7,845	6,748
Noninterest expense											55,689	49,268
Net income											$ 15,469	$ 9,170
Net income per common share											$ 1.84	$ 1.40