Condensed Financial Information - Parent Company Only - Schedule of Condensed Balance Sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Jan. 01, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Assets:
Cash and due from banks	$ 32,356		$ 31,995	$ 32,646	$ 98,399
Investments in subsidiaries, at equity in net assets:
Total assets	2,879,451		2,235,321
Liabilities:
Subordinated notes	49,377		0
Other liabilities	49,929		47,452
Total liabilities	2,517,877		1,950,767
Shareholders' equity:	361,574		284,554	280,506	284,277
Total liabilities and shareholders’ equity	2,879,451		2,235,321
Common Stock, Value, Issued acquisition of Valley Green	110,271		91,332
Parent Company [Member]
Assets:
Cash and due from banks	17,096		3,120	$ 2,999	$ 12,556
Investments in securities	807		1,336
Investments in subsidiaries, at equity in net assets:
Bank	392,304		283,166
Non-banks	0		0
Other assets	24,950		21,115
Total assets	435,157		308,737
Liabilities:
Dividends payable	3,905		3,243
Subordinated notes	49,377		0
Other liabilities	20,301		20,940
Total liabilities	73,583		24,183
Shareholders' equity:	361,574		284,554
Total liabilities and shareholders’ equity	$ 435,157		$ 308,737
Valley Green Bank [Member] | Parent Company [Member]
Liabilities:
Common Stock, Value, Issued acquisition of Valley Green		$ 77,000