Acquisition - Supplemental Pro Forma Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings per share
Restructuring charges	$ 0	$ 0	$ 1,642	$ 0
Branch optimization plan, restructuring charges, net of tax			$ 1,100
Branch optimization plan, restructuring charges, earnings per share, diluted			$ 0.05
Valley Green Bank [Member]
Business Acquisition [Line Items]
Net interest income	23,365	23,360	$ 70,049	69,005
Noninterest income	12,855	12,671	39,637	37,036
Noninterest expense	25,243	25,002	79,486	72,563
Net income	$ 7,528	$ 7,605	$ 20,110	$ 21,508
Earnings per share
Basic (in dollars per share)	$ 0.39	$ 0.38	$ 1.02	$ 1.07
Diluted (in dollars per share)	$ 0.39	$ 0.38	$ 1.02	$ 1.07
Integration and acquisition-related costs, gross			$ 2,000
Integration and acquisition-related costs, net of tax			$ 1,300
Integration and acquisition-related costs, earnings per share, diluted			$ 0.07