Junior Subordinated Debt - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) Location Trust	Dec. 31, 2017 USD ($)
Class of Stock [Line Items]
Number of subsidiary business trusts | Trust	5
Trust preferred securities amount | $
Number of locations organized | Location	2
Wholly Owned Subsidiaries [Member]
Class of Stock [Line Items]
Trust preferred securities amount | $	$ 62.9
Maximum [Member]
Class of Stock [Line Items]
Consecutive payments of interest on debenture defer Period	5 years
North Valley Bancorp [Member]
Class of Stock [Line Items]
Number of locations acquired | Location	3