Investment Securities - Age of Unrealized Losses and Fair Value of Related Securities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	$ 559,333	$ 374,643
Less than Twelve Months, Unrealized Losses	(38,574)	(4,118)
More than Twelve Months, Fair Value	56,475	63,882
More than Twelve Months, Unrealized Losses	(7,688)	(15,361)
Total, Fair Value	615,808	438,525
Total, Unrealized Losses	(46,262)	(19,479)
U.S. Treasury securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	84,665	97,625
Less than Twelve Months, Unrealized Losses	(15,170)	(2,218)
More than Twelve Months, Fair Value
More than Twelve Months, Unrealized Losses
Total, Fair Value	84,665	97,625
Total, Unrealized Losses	(15,170)	(2,218)
U.S. government agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	26,402
Less than Twelve Months, Unrealized Losses	(703)
More than Twelve Months, Fair Value
More than Twelve Months, Unrealized Losses
Total, Fair Value	26,402
Total, Unrealized Losses	(703)
Obligations of states and state agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	10,598
Less than Twelve Months, Unrealized Losses	(798)
More than Twelve Months, Fair Value
More than Twelve Months, Unrealized Losses
Total, Fair Value	10,598
Total, Unrealized Losses	(798)
Municipal bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	13,461
Less than Twelve Months, Unrealized Losses	(1,365)
More than Twelve Months, Fair Value
More than Twelve Months, Unrealized Losses
Total, Fair Value	13,461
Total, Unrealized Losses	(1,365)
Obligations of states and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	24,059
Less than Twelve Months, Unrealized Losses	(2,163)
More than Twelve Months, Fair Value
More than Twelve Months, Unrealized Losses
Total, Fair Value	24,059
Total, Unrealized Losses	(2,163)
Residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	368,306	269,895
Less than Twelve Months, Unrealized Losses	(18,434)	(1,256)
More than Twelve Months, Fair Value	24,734	21,089
More than Twelve Months, Unrealized Losses	(2,285)	(2,103)
Total, Fair Value	393,040	290,984
Total, Unrealized Losses	(20,719)	(3,359)
Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	2,024	760
Less than Twelve Months, Unrealized Losses	(25)	(511)
More than Twelve Months, Fair Value	15,022	27,865
More than Twelve Months, Unrealized Losses	(4,206)	(11,228)
Total, Fair Value	17,046	28,625
Total, Unrealized Losses	(4,231)	(11,739)
Corporate and other debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	53,654	5,394
Less than Twelve Months, Unrealized Losses	(2,073)	(58)
More than Twelve Months, Fair Value	2,471	2,264
More than Twelve Months, Unrealized Losses	(30)	(236)
Total, Fair Value	56,125	7,658
Total, Unrealized Losses	(2,103)	(294)
Equity securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	223	969
Less than Twelve Months, Unrealized Losses	(6)	(75)
More than Twelve Months, Fair Value	14,248	12,664
More than Twelve Months, Unrealized Losses	(1,167)	(1,794)
Total, Fair Value	14,471	13,633
Total, Unrealized Losses	$ (1,173)	$ (1,869)