Fair Value of Financial Instruments - Significant Inputs Used for Assets Measured at Fair Value on a Nonrecurring Basis (Detail)	12 Months Ended
	Dec. 31, 2015
Impaired loans
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Input	External appraised values- adjustments made to values due to management factors including age of appraisal, age of comparables, known changes in the market and in the collateral and selling and commission cost of 15% to 35%.
Method	Appraised Values
Impaired loans | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Adjustment for differences between comparable sales	15.00%
Impaired loans | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Adjustment for differences between comparable sales	35.00%
Mortgage Servicing Rights
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Input	Weighted average prepayment speed 11.31%; weighted average discount rate 11.35%.
Method	Discounted Cash Flow
Total portfolio lifetime weighted average prepayment speeds	11.31%
Weighted average discount rate	11.35%
Mortgage Servicing Rights | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Weighted average discount rate	11.00%
Mortgage Servicing Rights | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Weighted average discount rate	20.00%
Other Real Estate Owned
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Input	External appraised values less selling and commission cost of 15% to 35%.
Method	Appraised Values
Other Real Estate Owned | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Adjustment for differences between comparable sales	15.00%
Other Real Estate Owned | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Adjustment for differences between comparable sales	35.00%