Past Due Loans, Allowance For Credit Losses, Impaired Loans, and TDRs (Detail) - Credit Quality Indicators by Class, Excluding Covered Loans (Continued) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Home equity
Credit Quality Indicators by Class, Excluding Covered Loans [Line Items]
Credit Quality Indicators by Class	$ 653,468	$ 543,185
1-4 family mortgages
Credit Quality Indicators by Class, Excluding Covered Loans [Line Items]
Credit Quality Indicators by Class	355,854	291,463
Installment
Credit Quality Indicators by Class, Excluding Covered Loans [Line Items]
Credit Quality Indicators by Class	137,602	76,032
Total consumer loans
Credit Quality Indicators by Class, Excluding Covered Loans [Line Items]
Credit Quality Indicators by Class	1,146,924	910,680
Performing | Home equity
Credit Quality Indicators by Class, Excluding Covered Loans [Line Items]
Credit Quality Indicators by Class	648,158	536,895
Performing | 1-4 family mortgages
Credit Quality Indicators by Class, Excluding Covered Loans [Line Items]
Credit Quality Indicators by Class	352,438	288,522
Performing | Installment
Credit Quality Indicators by Class, Excluding Covered Loans [Line Items]
Credit Quality Indicators by Class	137,582	75,989
Performing | Total consumer loans
Credit Quality Indicators by Class, Excluding Covered Loans [Line Items]
Credit Quality Indicators by Class	1,138,178	901,406
Non-accrual | Home equity
Credit Quality Indicators by Class, Excluding Covered Loans [Line Items]
Credit Quality Indicators by Class	5,310	6,290
Non-accrual | 1-4 family mortgages
Credit Quality Indicators by Class, Excluding Covered Loans [Line Items]
Credit Quality Indicators by Class	3,416	2,941
Non-accrual | Installment
Credit Quality Indicators by Class, Excluding Covered Loans [Line Items]
Credit Quality Indicators by Class	20	43
Non-accrual | Total consumer loans
Credit Quality Indicators by Class, Excluding Covered Loans [Line Items]
Credit Quality Indicators by Class	$ 8,746	$ 9,274