Disclosures about Fair Value of Assets and Liabilities - Qualitative Information about Unobservable Inputs Used in Recurring and Nonrecurring Level 3 Fair Value Measurements, Other than Goodwill (Detail) - Significant Unobservable Inputs (Level 3) [Member] - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Impaired Loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value	$ 1,379	$ 2,246
Valuation Technique	Collateral based measurement
Impaired loans	Discount to reflect current market conditions and ultimate collectability
Mortgage Servicing Rights [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value	$ 11,257	$ 11,174
Valuation Technique	Discounted cashflows
Impaired loans	Discount rate, Constant prepayment rate, Probability of default
Minimum [Member] | Impaired Loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount to reflect current market conditions and ultimate collectability	11.00%	10.00%
Minimum [Member] | Mortgage Servicing Rights [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount rate	11.00%	10.00%
Constant prepayment rate	4.00%	4.00%
Probability of default	1.00%	1.00%
Maximum [Member] | Impaired Loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount to reflect current market conditions and ultimate collectability	17.00%	16.00%
Maximum [Member] | Mortgage Servicing Rights [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount rate	17.00%	16.00%
Constant prepayment rate	8.00%	7.00%
Probability of default	11.00%	10.00%
Weighted Average [Member] | Impaired Loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount to reflect current market conditions and ultimate collectability	14.00%	13.00%
Weighted Average [Member] | Mortgage Servicing Rights [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount rate	14.00%	13.00%
Constant prepayment rate	5.10%	4.60%
Probability of default	5.00%	4.50%