Fair Value Measurements - Additional Information (Detail) (USD $)	6 Months Ended
	Jun. 30, 2012 SimulationPath		Dec. 31, 2011
Fair Value, Measurement Inputs, Disclosure [Line Items]
Amortized Cost	$ 100,992,000		$ 149,987,000
Gross Unrealized Loss	2,208,000		2,804,000
Estimated Fair Value	99,111,000		147,909,000
Fair Value Asset Transfers Out of Level Three, Into Level Two | Collateralized mortgage obligations issued by non-agency
Fair Value, Measurement Inputs, Disclosure [Line Items]
Amortized Cost	669,000
Gross Unrealized Loss	12,000
Estimated Fair Value	657,000
Asset backed securities
Fair Value, Measurement Inputs, Disclosure [Line Items]
Number of default paths generated using Monte Carlo simulation	10,000
Recovery rate	0.00%
Prepayment rate	0.00%
Amortized Cost	2,247,000	[1]	2,324,000
Gross Unrealized Loss	2,010,000	[1]	1,944,000
Estimated Fair Value	$ 237,000	[1]	$ 380,000
Asset backed securities | Same industry
Fair Value, Measurement Inputs, Disclosure [Line Items]
Asset correlation for issuers	50.00%
Asset backed securities | Different industries
Fair Value, Measurement Inputs, Disclosure [Line Items]
Asset correlation for issuers	30.00%

[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