Loans and Allowance for Credit Losses - Troubled Debt Restructuring is 90 Days or More Past Due (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($) Contract	Sep. 30, 2015 USD ($) Contract	Sep. 30, 2016 USD ($) Contract	Sep. 30, 2015 USD ($) Contract
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | Contract	0	2	0	3
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | $	$ 0	$ 105	$ 0	$ 108
Residential real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | Contract	0	2	0	3
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | $	$ 0	$ 105	$ 0	$ 108