Investment Securities - Amortized Cost, Gross Unrealized Gains and Losses and Fair Value of Investment 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	$ 866,904	$ 813,474
Gross Unrealized Gains	9,050	13,821
Gross Unrealized Losses	(46,262)	(19,479)
Fair Value	829,692	807,816
U.S. Treasury securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	99,835	99,843
Gross Unrealized Gains
Gross Unrealized Losses	(15,170)	(2,218)
Fair Value	84,665	97,625
U.S. government agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	48,407	44,215
Gross Unrealized Gains	923	1,547
Gross Unrealized Losses	(703)
Fair Value	48,627	45,762
Obligations of states and state agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	11,441	207
Gross Unrealized Gains		6
Gross Unrealized Losses	(798)
Fair Value	10,643	213
Municipal bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	27,671	16,003
Gross Unrealized Gains	751	411
Gross Unrealized Losses	(1,365)
Fair Value	27,057	16,414
Obligations of states and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	39,112	16,210
Gross Unrealized Gains	751	417
Gross Unrealized Losses	(2,163)
Fair Value	37,700	16,627
Residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	524,781	506,695
Gross Unrealized Gains	3,967	6,818
Gross Unrealized Losses	(20,719)	(3,359)
Fair Value	508,029	510,154
Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	23,333	68,931
Gross Unrealized Gains	113	240
Gross Unrealized Losses	(4,231)	(11,739)
Fair Value	19,215	57,432
Corporate and other debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	83,819	28,274
Gross Unrealized Gains	1,682	2,728
Gross Unrealized Losses	(2,103)	(294)
Fair Value	83,398	30,708
Equity securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	47,617	49,306
Gross Unrealized Gains	1,614	2,071
Gross Unrealized Losses	(1,173)	(1,869)
Fair Value	$ 48,058	$ 49,508