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, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 29,574	$ 27,289	$ 24,943	$ 24,793
Total gains or losses included in earnings	0	242	77	625
Total gains or losses included in other comprehensive income	1,470	1,716	7,266	7,399
Purchases	0	0	0	0
Issuances	0	0	0	0
Sales	0	242	(3,112)	(20,760)
Settlements	168	2,128	(1,333)	(5,315)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3			3,035	20,135
Balance, end of period	30,876	26,877	30,876	26,877
Pooled Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	28,154	25,869	23,523	23,373
Total gains or losses included in earnings	0	0	0	0
Total gains or losses included in other comprehensive income	1,470	1,716	7,266	7,399
Purchases	0	0	0	0
Issuances	0	0	0	0
Sales	0	0	0	0
Settlements	168	2,128	(1,333)	(5,315)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3			0	0
Balance, end of period	29,456	25,457	29,456	25,457
Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	1,420	1,420	1,420	1,420
Total gains or losses included in earnings	0	0	0	0
Total gains or losses included in other comprehensive income	0	0	0	0
Purchases	0	0	0	0
Issuances	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3			0	0
Balance, end of period	1,420	1,420	1,420	1,420
Loans Held For Sale [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	0	0	0	0
Total gains or losses included in earnings	0	242	77	625
Total gains or losses included in other comprehensive income	0	0	0	0
Purchases	0	0	0	0
Issuances	0	0	0	0
Sales	0	242	(3,112)	(20,760)
Settlements	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3			3,035	20,135
Balance, end of period	0	0	0	0
Other Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	0	0	0	0
Total gains or losses included in earnings	0	0	0	0
Total gains or losses included in other comprehensive income	0	0	0	0
Purchases	0	0	0	0
Issuances	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3			0	0
Balance, end of period	$ 0	$ 0	$ 0	$ 0