Parent Company Only Financial Information - Condensed Statements of Income (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Dividends from:
Income tax benefit									$ 7,171	$ 8,292	$ 9,314
Net Income	$ 5,040	$ 6,416	$ 4,065	$ 5,019	$ 5,508	$ 5,522	$ 5,602	$ 5,565	20,540	22,197	23,074
Parent Company [Member]
Dividends from:
Bank subsidiary									8,700	10,404	10,675
Non-bank subsidiaries									1,200	323	0
Other									230	157	170
Total income									10,130	10,884	10,845
Expenses									(2,611)	(1,708)	(1,520)
Income before income taxes and equity in undistributed net income of subsidiaries:									7,519	9,176	9,325
Income tax benefit									813	547	473
Equity in undistributed net income of bank subsidiary									13,184	11,889	12,327
Equity in undistributed net income (loss) of non-bank subsidiaries									(976)	585	949
Net Income									$ 20,540	$ 22,197	$ 23,074