Investment Securities - Amortized Cost, Gross Unrealized Gains and Losses and Fair Value of Securities Available for Sale (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 821,322	$ 866,904
Gross Unrealized Gains	8,526	9,050
Gross Unrealized Losses	(33,265)	(46,262)
Fair Value	796,583	829,692
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	99,833	99,835
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(10,962)	(15,170)
Fair Value	88,871	84,665
U.S. Government Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	47,118	48,407
Gross Unrealized Gains	866	923
Gross Unrealized Losses	(453)	(703)
Fair Value	47,531	48,627
Obligations of States and State Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	11,338	11,441
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(516)	(798)
Fair Value	10,822	10,643
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	27,664	27,671
Gross Unrealized Gains	99	751
Gross Unrealized Losses	(761)	(1,365)
Fair Value	27,002	27,057
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	39,002	39,112
Gross Unrealized Gains	99	751
Gross Unrealized Losses	(1,277)	(2,163)
Fair Value	37,824	37,700
Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	506,034	524,781
Gross Unrealized Gains	3,835	3,967
Gross Unrealized Losses	(14,265)	(20,719)
Fair Value	495,604	508,029
Trust Preferred Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	23,298	23,333
Gross Unrealized Gains	198	113
Gross Unrealized Losses	(3,890)	(4,231)
Fair Value	19,606	19,215
Corporate and Other Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	83,464	83,819
Gross Unrealized Gains	1,893	1,682
Gross Unrealized Losses	(1,267)	(2,103)
Fair Value	84,090	83,398
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	22,573	47,617
Gross Unrealized Gains	1,635	1,614
Gross Unrealized Losses	(1,151)	(1,173)
Fair Value	$ 23,057	$ 48,058