Parent Company Only Financial Information - Condensed Statements of Income (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Dividends from:
Income tax benefit									$ 8,292	$ 9,314	$ 6,340
Net Income	$ 5,508	$ 5,522	$ 5,602	$ 5,565	$ 6,743	$ 5,548	$ 5,617	$ 5,166	22,197	23,074	16,679
Parent Company [Member]
Dividends from:
Bank subsidiary									10,404	10,675	1,875
Non-bank subsidiaries									323	0	6,674
Other									157	170	208
Total income									10,884	10,845	8,757
Expenses									(1,708)	(1,520)	(1,461)
Income before income taxes and equity in undistributed net income of subsidiaries:									9,176	9,325	7,296
Income tax benefit									547	473	438
Equity in undistributed net income of bank subsidiary									11,889	12,327	14,080
Equity in undistributed net income (loss) of non-bank subsidiaries									585	949	(5,135)
Net Income									$ 22,197	$ 23,074	$ 16,679