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) - Discounted Cash Flow - Residential mortgage-backed securities	12 Months Ended
	Dec. 31, 2016
Fair Value Assets Measured On Recurring Basis [Line Items]
Prepayment rate, Weighted Average of unobservable inputs	19.10%
Default rate, Weighted Average of unobservable inputs	9.00%
Loss severity, Weighted Average of unobservable inputs	60.00%
Minimum
Fair Value Assets Measured On Recurring Basis [Line Items]
Prepayment rate, Range of unobservable inputs	15.00%
Default rate, Range of unobservable inputs	3.60%
Loss severity, Range of unobservable inputs	45.60%
Maximum
Fair Value Assets Measured On Recurring Basis [Line Items]
Prepayment rate, Range of unobservable inputs	22.50%
Default rate, Range of unobservable inputs	33.20%
Loss severity, Range of unobservable inputs	66.00%