Condensed Financial Information - Parent Company Only - Schedule of Condensed Income Statement (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statements of Income
Other-than-temporary impairment on equity securities										$ (13)	$ (16)
Net gain on sales of investment securities									3,389	305	1,417
Loss on termination of interest rate swap									(1,866)
Income before income taxes	5,971	7,439	6,367	7,108	6,434	7,612	6,168	6,209	26,885	26,423	23,658
Income tax benefit	1,049	1,400	1,537	1,710	1,358	1,842	1,405	946	5,696	5,551	4,776
Equity in undistributed income (loss) of subsidiaries:
Net income	4,922	6,039	4,830	5,398	5,076	5,770	4,763	5,263	21,189	20,872	18,882
Parent Company [Member]
Statements of Income
Dividends from bank									18,482	20,482	12,482
Dividends from non-banks										1,200	1,190
Other-than-temporary impairment on equity securities										(13)	(16)
Net gain on sales of investment securities									644	70	58
Loss on termination of interest rate swap									(1,866)
Other income									18,306	17,463	14,986
Total operating income									35,566	39,202	28,700
Operating expenses									19,203	18,323	16,946
Income before income taxes									16,363	20,879	11,754
Income tax benefit									(903)	(143)	(547)
Income before equity in undistributed income (loss) of subsidiaries									17,266	21,022	12,301
Equity in undistributed income (loss) of subsidiaries:
Bank									3,929	(140)	6,576
Non-banks									(6)	(10)	5
Net income									$ 21,189	$ 20,872	$ 18,882