Fair Value Measurement of Assets and Liabilities - Schedule of Quantitative Information About Level 3 Inputs Used to Measure the Fair Value of Available For Sale Securities (Detail)	12 Months Ended
	Dec. 31, 2012
Residential mortgage-backed securities [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Prepayment rate, Weighted Average of unobservable inputs	15.90%
Default rate, Weighted Average of unobservable inputs	8.00%
Loss severity, Weighted Average of unobservable inputs	50.90%
Trust preferred securities [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Loss severity, Weighted Average of unobservable inputs	28.80%
Market credit spreads, Weighted Average of unobservable inputs	6.70%
Discount rate, Weighted Average of unobservable inputs	7.80%
Minimum [Member] | Residential mortgage-backed securities [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Prepayment rate, Range of unobservable inputs	2.70%
Default rate, Range of unobservable inputs	4.00%
Loss severity, Range of unobservable inputs	40.00%
Minimum [Member] | Trust preferred securities [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Loss severity, Range of unobservable inputs	0.00%
Market credit spreads, Range of unobservable inputs	6.30%
Discount rate, Range of unobservable inputs	6.60%
Maximum [Member] | Residential mortgage-backed securities [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Prepayment rate, Range of unobservable inputs	27.40%
Default rate, Range of unobservable inputs	17.20%
Loss severity, Range of unobservable inputs	59.40%
Maximum [Member] | Trust preferred securities [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Loss severity, Range of unobservable inputs	100.00%
Market credit spreads, Range of unobservable inputs	6.90%
Discount rate, Range of unobservable inputs	8.70%