Other Liabilities - Components of Other Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other Liabilities Disclosure [Abstract]
Deferred compensation	$ 6,605	$ 6,525
Pension liability	28,472	26,645
Joint beneficiary agreements	3,365	3,007
Low income housing tax credit fund commitments	8,554	15,176
Accrued salaries and benefits expense	6,619	5,704
Loan escrow and servicing payable	1,958	2,146
Deferred revenue	1,228	726
Litigation contingency	1,450	1,450
Miscellaneous other liabilities	5,007	5,985
Total other liabilities	$ 63,258	$ 67,364