Investment Securities - Additional Information (Detail) (USD $)	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Other investments	$ 44,077,000		$ 35,444,000
Amortized Cost	1,357,315,000		1,350,466,000
Available-for-sale Securities	1,347,611,000		1,318,365,000
Proceeds from the redemption of FHLB stock	10,025,000	4,984,000
Available-for-sale securities pledged as collateral	511,900,000		594,900,000
Corporate Debt Securities [Member]
Amortized Cost	6,688,000		6,693,000
Available-for-sale Securities	$ 7,249,000		$ 7,021,000