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, 2016	Mar. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 37,828	$ 30,419
Total gains or losses included in earnings	0	105
Total gains or losses included in other comprehensive income	(2,385)	2,620
Purchases	36	500
Issuances	0	0
Sales	0	0
Settlements	0	(590)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	0
Balance, end of period	35,479	33,054
Pooled Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	35,658	28,999
Total gains or losses included in earnings	0	105
Total gains or losses included in other comprehensive income	(2,385)	2,620
Purchases	0	0
Issuances	0	0
Sales	0	0
Settlements	0	(590)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	0
Balance, end of period	33,273	31,134
Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	2,170	1,420
Total gains or losses included in earnings	0	0
Total gains or losses included in other comprehensive income	0	0
Purchases	36	500
Issuances	0	0
Sales	0	0
Settlements	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	0
Balance, end of period	$ 2,206	$ 1,920