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	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	$ 117,835	$ 341,633
Less than 12 Months, Unrealized Loss	(961)	(16,734)
12 Months or More, Fair Value	240,321	58,496
12 Months or More, Unrealized Loss	(7,543)	(4,840)
Total, Fair Value	358,156	400,129
Total, Unrealized Loss	(8,504)	(21,574)
U.S. Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	26,069	95,677
Less than 12 Months, Unrealized Loss	(149)	(5,394)
12 Months or More, Fair Value	85,016	17,964
12 Months or More, Unrealized Loss	(2,070)	(1,080)
Total, Fair Value	111,085	113,641
Total, Unrealized Loss	(2,219)	(6,474)
States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	16,398	57,526
Less than 12 Months, Unrealized Loss	(179)	(2,192)
12 Months or More, Fair Value	12,363	5,324
12 Months or More, Unrealized Loss	(223)	(125)
Total, Fair Value	28,761	62,850
Total, Unrealized Loss	(402)	(2,317)
Residential and Multi-Family Mortgage [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	70,360	150,229
Less than 12 Months, Unrealized Loss	(603)	(6,806)
12 Months or More, Fair Value	99,397	16,608
12 Months or More, Unrealized Loss	(2,202)	(1,014)
Total, Fair Value	169,757	166,837
Total, Unrealized Loss	(2,805)	(7,820)
Commercial Mortgage [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value		374
Less than 12 Months, Unrealized Loss		(11)
12 Months or More, Fair Value		0
12 Months or More, Unrealized Loss		0
Total, Fair Value		374
Total, Unrealized Loss		(11)
Corporate Notes and Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	5,008	0
Less than 12 Months, Unrealized Loss	(30)	0
12 Months or More, Fair Value	7,935	9,662
12 Months or More, Unrealized Loss	(1,470)	(1,734)
Total, Fair Value	12,943	9,662
Total, Unrealized Loss	(1,500)	(1,734)
Pooled Trust Preferred [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value		0
Less than 12 Months, Unrealized Loss		0
12 Months or More, Fair Value		661
12 Months or More, Unrealized Loss		(139)
Total, Fair Value		661
Total, Unrealized Loss		(139)
Pooled SBA [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	0	36,842
Less than 12 Months, Unrealized Loss	0	(2,296)
12 Months or More, Fair Value	34,608	8,277
12 Months or More, Unrealized Loss	(1,560)	(748)
Total, Fair Value	34,608	45,119
Total, Unrealized Loss	(1,560)	(3,044)
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	0	985
Less than 12 Months, Unrealized Loss	0	(35)
12 Months or More, Fair Value	1,002	0
12 Months or More, Unrealized Loss	(18)	0
Total, Fair Value	1,002	985
Total, Unrealized Loss	$ (18)	$ (35)

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