Shareholders' Equity and Earnings Per Share - Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of factors used in computing basic and diluted earnings per common share
Net income	$ 5,685	$ 11,277	$ 11,353	$ 12,146	$ 13,232	$ 12,375	$ 915	$ 8,809	$ 40,461	$ 35,331	$ 23,828
Weighted average common shares outstanding for basic earnings per common share (in shares)									46,684,384	41,469,211	38,095,250
Dilutive potential common shares									1,221,845	713,728	515,565
Shares used in computing diluted earnings per common share (in shares)									47,906,229	42,182,939	38,610,815
Basic earnings per share (in dollars per share)	$ 0.10	$ 0.26	$ 0.26	$ 0.28	$ 0.31	$ 0.29	$ 0.02	$ 0.23	$ 0.87	$ 0.85	$ 0.63
Diluted earnings per share (in dollars per share)	$ 0.10	$ 0.26	$ 0.26	$ 0.28	$ 0.30	$ 0.28	$ 0.02	$ 0.23	$ 0.84	$ 0.84	$ 0.62
Number of shares not in computing diluted earnings per common share									789,065	534,106	346,500