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)	3 Months Ended
	Mar. 31, 2013
Residential mortgage-backed securities [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Prepayment rate, Weighted Average of unobservable inputs	16.10%
Default rate, Weighted Average of unobservable inputs	7.60%
Loss severity, Weighted Average of unobservable inputs	51.30%
Trust preferred securities [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Loss severity, Weighted Average of unobservable inputs	21.60%
Market credit spreads, Weighted Average of unobservable inputs	6.00%
Discount rate, Weighted Average of unobservable inputs	7.20%
Minimum [Member] | Residential mortgage-backed securities [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Prepayment rate, Range of unobservable inputs	11.20%
Default rate, Range of unobservable inputs	4.50%
Loss severity, Range of unobservable inputs	40.30%
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	5.60%
Discount rate, Range of unobservable inputs	5.90%
Maximum [Member] | Residential mortgage-backed securities [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Prepayment rate, Range of unobservable inputs	23.30%
Default rate, Range of unobservable inputs	16.40%
Loss severity, Range of unobservable inputs	59.70%
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	6.20%
Discount rate, Range of unobservable inputs	8.10%