Condensed Financial Information - Parent Company Only - Schedule of Condensed Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Assets:
Cash and due from banks	$ 31,995	$ 32,646	$ 98,399	$ 39,857
Investments in subsidiaries, at equity in net assets:
Total assets	2,235,321	2,191,559
Liabilities:
Other liabilities	47,452	29,299
Total liabilities	1,950,767	1,911,053
Shareholders' equity:	284,554	280,506	284,277	272,979
Total liabilities and shareholders’ equity	2,235,321	2,191,559
Parent Company [Member]
Assets:
Cash and due from banks	3,120	2,999	12,556	2,554
Investments in securities	1,336	2,347
Investments in subsidiaries, at equity in net assets:
Bank	283,166	271,147
Non-banks	0	0
Other assets	21,115	17,658
Total assets	308,737	294,151
Liabilities:
Dividends payable	3,243	3,257
Other liabilities	20,940	10,388
Total liabilities	24,183	13,645
Shareholders' equity:	284,554	280,506
Total liabilities and shareholders’ equity	$ 308,737	$ 294,151