Investment Securities Available For Sale - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended				1 Months Ended	3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Mar. 31, 2013	Dec. 31, 2012	Nov. 30, 2007 Asset backed security Entity Investment	Jun. 30, 2012 Asset backed security	Jun. 30, 2013 Asset backed security		Dec. 31, 2012 Asset backed security
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair market value of securities pledged as collateral	$ 13,000,000		$ 13,000,000			$ 10,000,000
Net gains on sales of securities available for sale			23,000	12,000,000
Proceeds from sale of securities available for sale			6,200,000	136,000,000
Portion of other-than-temporary impairment losses recognized in other comprehensive loss	1,413,000		1,413,000		(1,308,000)	(1,264,000)
Number of securities							1
Trust preferred securities, number of issuers							56
Trust preferred securities, number of U.S. depository institutions							45
Trust preferred securities, number of insurance companies							11
Trust preferred securities issued, value							363,000,000
Basis points over 3 months LIBOR							60.00%
Available for sale security purchased, face value							3,000,000
Available for sale security purchased, price as percentage of face amount							95.21%
Available for sale security purchased, price paid							2,900,000
Amortized Cost	73,672,000		73,672,000			87,306,000			2,247,000	[1]	2,247,000	[1]
Estimated Fair Value	69,950,000		69,950,000			86,378,000			775,000	[1]	900,000	[1]
Gross Unrealized Loss	3,804,000		3,804,000			1,568,000			1,472,000	[1]	1,347,000	[1]
Available-for-sale securities, default experienced									42,500,000
Percentage of default to total current collateral									12.50%
Security payment deferrals									43,500,000
Percentage of payment deferrals to total current collateral									12.80%
Estimated additional defaults									72,500,000
Assumption in estimating security defaults, future default rates									2.50%
Fair value inputs, prepayment rate									1.00%
Fair value inputs, recovery rate									15.00%
Impairment loss on securities	$ 0		$ 0	$ 77,000				$ 77,000

[1] Comprised of a security that represents an interest in a pool of trust preferred securities issued by U.S.-based banks and insurance companies.