Securities - Securities with Unrealized Losses Aggregated by Investment Category and Length of Time that Individual Securities have been in Continuous Unrealized Loss Position (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	$ 369,935	$ 85,252
Less than 12 Months, Unrealized Loss	(17,046)	(923)
12 Months or More, Fair Value	17,930	17,856
12 Months or More, Unrealized Loss	(1,974)	(2,584)
Total, Fair Value	387,865	103,108
Total, Unrealized Loss	(19,020)	(3,507)
U.S. Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	0	0
Less than 12 Months, Unrealized Loss	0	0
12 Months or More, Fair Value	0	0
12 Months or More, Unrealized Loss	0	0
Total, Fair Value	0	0
Total, Unrealized Loss	0	0
U.S. Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	110,419	41,715
Less than 12 Months, Unrealized Loss	(5,820)	(161)
12 Months or More, Fair Value	0	0
12 Months or More, Unrealized Loss	0	0
Total, Fair Value	110,419	41,715
Total, Unrealized Loss	(5,820)	(161)
States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	58,955	7,857
Less than 12 Months, Unrealized Loss	(2,047)	(57)
12 Months or More, Fair Value	474	0
12 Months or More, Unrealized Loss	(9)	0
Total, Fair Value	59,429	7,857
Total, Unrealized Loss	(2,056)	(57)
Residential and Multi Family Mortgage [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	157,880	32,159
Less than 12 Months, Unrealized Loss	(6,201)	(688)
12 Months or More, Fair Value	5,124	4,254
12 Months or More, Unrealized Loss	(171)	(14)
Total, Fair Value	163,004	36,413
Total, Unrealized Loss	(6,372)	(702)
Commercial Mortgage [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	950	0
Less than 12 Months, Unrealized Loss	(21)	0
12 Months or More, Fair Value	0	0
12 Months or More, Unrealized Loss	0	0
Total, Fair Value	950	0
Total, Unrealized Loss	(21)	0
Corporate Notes and Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	0	0
Less than 12 Months, Unrealized Loss	0	0
12 Months or More, Fair Value	9,754	13,002
12 Months or More, Unrealized Loss	(1,640)	(2,370)
Total, Fair Value	9,754	13,002
Total, Unrealized Loss	(1,640)	(2,370)
Pooled Trust Preferred [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	0	0
Less than 12 Months, Unrealized Loss	0	0
12 Months or More, Fair Value	776	600
12 Months or More, Unrealized Loss	(24)	(200)
Total, Fair Value	776	600
Total, Unrealized Loss	(24)	(200)
Pooled SBA [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	40,735	3,521
Less than 12 Months, Unrealized Loss	(2,933)	(17)
12 Months or More, Fair Value	1,802	0
12 Months or More, Unrealized Loss	(130)	0
Total, Fair Value	42,537	3,521
Total, Unrealized Loss	(3,063)	(17)
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	996	0
Less than 12 Months, Unrealized Loss	(24)	0
12 Months or More, Fair Value	0	0
12 Months or More, Unrealized Loss	0	0
Total, Fair Value	996	0
Total, Unrealized Loss	$ (24)	$ 0