Derivative Financial Instruments - Schedule of Notional Amounts and Estimated Fair Values of Interest Rate Derivative Contracts Outstanding (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Designated as Hedging Instrument [Member] | Financial institution counterparties Loan/lease interest rate swaps assets [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	$ 46,939	$ 14,748
Estimated Fair Value	1,023	24
Designated as Hedging Instrument [Member] | Financial institution counterparties Loan/lease interest rate swaps liabilities [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	49,396	84,577
Estimated Fair Value	(4,777)	(7,186)
Designated as Hedging Instrument [Member] | Interest rate swap on junior subordinated deferrable interest debentures [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	120,000	120,000
Estimated Fair Value	(1,098)	(4,365)
Non Designated as Hedging Instrument [Member] | Financial institution counterparties Loan/lease interest rate swaps assets [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	191,770	0
Estimated Fair Value	6,533	0
Non Designated as Hedging Instrument [Member] | Financial institution counterparties Loan/lease interest rate swaps liabilities [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	569,191	797,311
Estimated Fair Value	(37,462)	(60,994)
Non Designated as Hedging Instrument [Member] | Financial institution counterparties Loan/lease interest-rate caps assets [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	53,058	30,000
Estimated Fair Value	1,120	12
Non Designated as Hedging Instrument [Member] | Customer counterparties Loan/lease interest rate swaps assets [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	569,191	797,311
Estimated Fair Value	37,406	60,854
Non Designated as Hedging Instrument [Member] | Customer counterparties Loan/lease interest rate swaps liabilities [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	191,770	0
Estimated Fair Value	(6,533)	0
Non Designated as Hedging Instrument [Member] | Customer counterparties Loan/lease interest rate caps liabilities [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	53,058	30,000
Estimated Fair Value	$ (1,120)	$ (12)