Derivative Financial Instruments - Schedule of Notional Amounts and Estimated Fair Values of Interest Rate Derivative Contracts Outstanding (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Designated as Hedging Instrument [Member] | Financial institution counterparties Loan/lease interest rate swaps assets [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	$ 52,591	$ 31,614
Estimated Fair Value	568	469
Designated as Hedging Instrument [Member] | Financial institution counterparties Loan/lease interest rate swaps liabilities [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	33,240	37,672
Estimated Fair Value	(2,762)	(3,179)
Non Designated as Hedging Instrument [Member] | Financial institution counterparties Loan/lease interest rate swaps assets [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	202,633	69,842
Estimated Fair Value	1,293	719
Non Designated as Hedging Instrument [Member] | Financial institution counterparties Loan/lease interest rate swaps liabilities [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	639,808	765,979
Estimated Fair Value	(34,024)	(38,952)
Non Designated as Hedging Instrument [Member] | Financial institution counterparties Loan/lease interest-rate caps assets [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	87,339	73,058
Estimated Fair Value	1,143	1,003
Non Designated as Hedging Instrument [Member] | Customer counterparties Loan/lease interest rate swaps assets [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	639,808	765,979
Estimated Fair Value	33,985	38,910
Non Designated as Hedging Instrument [Member] | Customer counterparties Loan/lease interest rate swaps liabilities [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	202,633	69,842
Estimated Fair Value	(1,293)	(719)
Non Designated as Hedging Instrument [Member] | Customer counterparties Loan/lease interest rate caps liabilities [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	87,339	73,058
Estimated Fair Value	$ (1,143)	$ (1,003)