Noninterest Income and Expense - Components of Noninterest Expense (Detail) - USD ($) $ in Thousands	3 Months Ended						6 Months Ended
	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2016	Jun. 30, 2015
Schedule Of Other Noninterest Income And Expense [Line Items]
Base salaries, net of deferred loan origination costs	$ 12,968				$ 11,502		$ 25,676	$ 23,246
Incentive compensation	2,471				1,390		4,210	2,986
Benefits and other compensation costs	4,606				4,350		9,424	9,110
Total salaries and benefits expense	20,045				17,242		39,310	35,342
Occupancy	2,529				2,541		4,837	4,958
Equipment	1,844				1,527		3,230	2,941
Data processing and software	2,355				1,834		4,198	3,786
ATM network charges	1,002				985		2,008	1,755
Telecommunications	698				785		1,383	1,671
Postage	342				330		805	642
Courier service	265				253		536	501
Advertising	1,077				1,002		1,972	1,810
Assessments	578				694		1,210	1,345
Operational losses	345				149		509	273
Professional fees	1,356				1,035		2,165	2,154
Foreclosed assets expense	114				102		160	200
Provision for foreclosed asset losses	43				174		32	241
Reserve for unfunded commitments	408				110		408	(20)
Intangible amortization	359				289		658	578
Merger expense	162						784	586
Litigation contingent liability	1,450						1,450
Other	3,295				3,384		6,363	5,955
Total other noninterest expense	18,222				15,194		32,708	29,376
Total noninterest expense	38,267	$ 33,751	$ 34,684	$ 31,439	$ 32,436	$ 32,282	72,018	64,718
North Valley Bancorp [Member]
Schedule Of Other Noninterest Income And Expense [Line Items]
Base salaries (outside temporary help)							187
Data processing and software								108
Professional fees	162						342	120
Advertising and marketing							114
Merger expense	$ 162						784	586
Other							$ 141	$ 358