Valuation Techniques, Significant Unobservable Inputs, Quantitative Information Non-recurring Basis (Detail) - Fair Value, Measurements, Nonrecurring - Fair Value, Inputs, Level 3 - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value	$ 6.7	$ 10.4
Valuation Technique	Market Approach
Unobservable Input	Discount to reflect realizable value
Loans | Lower Limit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Range of Discounts Applied	15.00%
Loans | Upper Limit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Range of Discounts Applied	25.00%
OREO
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value	$ 0.7	$ 3.6
Valuation Technique	Market Approach
Unobservable Input	Discount to reflect realizable value
OREO | Lower Limit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Range of Discounts Applied	15.00%
OREO | Upper Limit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Range of Discounts Applied	20.00%