Securities - Amortized Cost and Estimated Fair Value of Securities Available for Sale (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-Sale Securities [Line Items]
Amortized Cost	$ 488,838	$ 336,710
Gross Unrealized Gains	4,891	11,166
Gross Unrealized Losses	(7,494)	(967)
Estimated Fair Value	486,235	346,909
U.S. Government Sponsored Agencies [Member]
Schedule of Available-for-Sale Securities [Line Items]
Amortized Cost	14,947	6,605
Gross Unrealized Gains		271
Gross Unrealized Losses	(1,021)	(6)
Estimated Fair Value	13,926	6,870
State, County and Municipal Securities [Member]
Schedule of Available-for-Sale Securities [Line Items]
Amortized Cost	112,659	109,736
Gross Unrealized Gains	2,269	4,864
Gross Unrealized Losses	(2,174)	(210)
Estimated Fair Value	112,754	114,390
Corporate Debt Securities [Member]
Schedule of Available-for-Sale Securities [Line Items]
Amortized Cost	10,311	10,545
Gross Unrealized Gains	275	330
Gross Unrealized Losses	(261)	(547)
Estimated Fair Value	10,325	10,328
Collateralized Debt Obligations [Member]
Schedule of Available-for-Sale Securities [Line Items]
Amortized Cost	1,480
Estimated Fair Value	1,480
Mortgage-Backed Securities [Member]
Schedule of Available-for-Sale Securities [Line Items]
Amortized Cost	349,441	209,824
Gross Unrealized Gains	2,347	5,701
Gross Unrealized Losses	(4,038)	(204)
Estimated Fair Value	$ 347,750	$ 215,321