Fair Values of Assets and Liabilities - Schedule of Changes in Level 3 Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 35,892	$ 37,828
Total gains or losses included in earnings	0	0
Total gains or losses included in other comprehensive income	497	(2,385)
Purchases	410	36
Issuances	0	0
Sales	0	0
Settlements	(48)	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	0
Balance, end of period	36,751	35,479
Pooled Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	33,292	35,658
Total gains or losses included in earnings	0	0
Total gains or losses included in other comprehensive income	497	(2,385)
Purchases	0	0
Issuances	0	0
Sales	0	0
Settlements	(48)	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	0
Balance, end of period	33,741	33,273
Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	1,670	2,170
Total gains or losses included in earnings	0	0
Total gains or losses included in other comprehensive income	0	0
Purchases	0	36
Issuances	0	0
Sales	0	0
Settlements	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	0
Balance, end of period	1,670	$ 2,206
Other Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	930
Total gains or losses included in earnings	0
Total gains or losses included in other comprehensive income	0
Purchases	410
Issuances	0
Sales	0
Settlements	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0
Balance, end of period	$ 1,340