Other Liabilities - Components of Other Liabilities (Detail) - USD ($)	Sep. 30, 2015	Dec. 31, 2014
Other Liabilities Disclosure [Abstract]
Deferred compensation	$ 6,661,000	$ 7,408,000
Pension liability	27,338,000	26,798,000
Joint beneficiary agreements	2,900,000	2,728,000
Low income housing tax credit fund commitments	3,651,000	0
Accrued salaries & benefits expense	3,899,000	5,407,000
Taxes payable	2,276,000	0
Loan escrow and servicing payable	3,009,000	1,938,000
Deferred Revenue	1,341,000	1,091,000
Miscellaneous other liabilities	3,177,000	3,822,000
Total other liabilities	$ 54,252,000	$ 49,192,000