Balance Sheet Offsetting - Financial Instruments Eligible for Offset Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial assets	$ 12,458	$ 2,246
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	12,458	2,246
Gross Amount Recognized, Resell agreements, Financial assets	4,898	4,898
Gross Amount Offset, Resell agreements, Financial assets	0	0
Net Amount Recognized, Resell agreements, Financial assets	4,898	4,898
Gross Amount Recognized, Financial assets	17,356	7,144
Gross Amount Offset, Financial assets	0	0
Net Amount Recognized, Financial assets	17,356	7,144
Gross Amount Recognized, Derivatives, Financial liabilities	48,374	74,159
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	48,374	74,159
Gross Amount Recognized, Repurchase agreements, Financial liabilities	584,612	559,461
Gross Amount Offset, Repurchase agreements, Financial liabilities	0	0
Net Amount Recognized, Repurchase agreements, Financial liabilities	584,612	559,461
Gross Amount Recognized, Financial liabilities	632,986	633,620
Gross Amount Offset, Financial liabilities	0	0
Net Amount Recognized, Financial liabilities	632,986	633,620
Loan/lease interest rate swaps and caps [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial assets	8,676	36
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	8,676	36
Commodity swaps and options [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial assets	3,782	2,207
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	3,782	2,207
Gross Amount Recognized, Derivatives, Financial liabilities	4,689	1,614
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	4,689	1,614
Foreign currency forward contracts [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial assets	0	3
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	0	3
Gross Amount Recognized, Derivatives, Financial liabilities	348
Gross Amount Offset, Derivatives, Financial liabilities	0
Net Amount Recognized, Derivatives, Financial liabilities	348
Loan/lease interest rate swaps [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial liabilities	42,239	68,180
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	42,239	68,180
Interest rate swap on junior subordinated deferrable interest debentures [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial liabilities	1,098	4,365
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	$ 1,098	$ 4,365