Fair Value Measurement of Assets and Liabilities - Schedule of Quantitative Information about Level 3 Inputs Used to Measure Fair Value of Available for Sale Securities (Detail) (Significant Unobservable Inputs (Level 3) [Member], Residential Mortgage-Backed Securities [Member])	9 Months Ended
	Sep. 30, 2014
Fair Value Assets Measured On Recurring Basis [Line Items]
Valuation technique to measure fair value	Discounted cash flow
Prepayment rate, Weighted Average of unobservable inputs	11.20%
Default rate, Weighted Average of unobservable inputs	8.10%
Loss severity, Weighted Average of unobservable inputs	51.10%
Minimum [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Prepayment rate, Range of unobservable inputs	0.20%
Default rate, Range of unobservable inputs	2.90%
Loss severity, Range of unobservable inputs	41.60%
Maximum [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Prepayment rate, Range of unobservable inputs	42.30%
Default rate, Range of unobservable inputs	23.10%
Loss severity, Range of unobservable inputs	61.10%