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) - Residential mortgage-backed securities	9 Months Ended
	Sep. 30, 2015
Fair Value Assets Measured On Recurring Basis
Valuation technique to measure fair value	Discounted cash flow
Prepayment rate, Weighted Average of unobservable inputs	14.70%
Default rate, Weighted Average of unobservable inputs	8.50%
Loss severity, Weighted Average of unobservable inputs	57.70%
Minimum
Fair Value Assets Measured On Recurring Basis
Prepayment rate, Range of unobservable inputs	4.70%
Default rate, Range of unobservable inputs	3.50%
Loss severity, Range of unobservable inputs	39.20%
Maximum
Fair Value Assets Measured On Recurring Basis
Prepayment rate, Range of unobservable inputs	21.90%
Default rate, Range of unobservable inputs	20.40%
Loss severity, Range of unobservable inputs	64.20%