Balance Sheet Offsetting - Financial Instruments Eligible for Offset Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	$ 16,265	$ 2,246
Gross Amount Offset, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivative, Financial Assets	16,265	2,246
Gross Amount Recognized, Resell Agreements, Financial Assets	7,898	4,898
Gross Amount Offset, Resell Agreements, Financial Assets	0	0
Net Amount Recognized, Resell Agreements, Financial Assets	7,898	4,898
Gross Amount Recognized, Financial Assets	24,163	7,144
Gross Amount Offset, Financial Assets	0	0
Net Amount Recognized, Financial Assets	24,163	7,144
Gross Amount Recognized, Derivative, Financial Liabilities	42,603	74,159
Gross Amount Offset, Derivative, Financial Liabilities	0	0
Net Amount Recognized, Derivative, Financial Liabilities	42,603	74,159
Gross Amount Recognized, Repurchase Agreements, Financial Liabilities	668,053	559,461
Gross Amount Offset, Repurchase Agreements, Financial Liabilities	0	0
Net Amount Recognized, Repurchase Agreements, Financial Liabilities	668,053	559,461
Gross Amount Recognized, Financial Liabilities	710,656	633,620
Gross Amount Offset, Financial Liabilities	0	0
Net Amount Recognized, Financial Liabilities	710,656	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	12,268	36
Gross Amount Offset, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivative, Financial Assets	12,268	36
Commodity Swaps And Options [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	3,907	2,207
Gross Amount Offset, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivative, Financial Assets	3,907	2,207
Gross Amount Recognized, Derivative, Financial Liabilities	5,916	1,614
Gross Amount Offset, Derivative, Financial Liabilities	0	0
Net Amount Recognized, Derivative, Financial Liabilities	5,916	1,614
Foreign Currency Forward Contracts [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	90	3
Gross Amount Offset, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivative, Financial Assets	90	3
Gross Amount Recognized, Derivative, Financial Liabilities	27
Gross Amount Offset, Derivative, Financial Liabilities	0
Net Amount Recognized, Derivative, Financial Liabilities	27
Loan Lease Interest Rate Swaps [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivative, Financial Liabilities	36,660	68,180
Gross Amount Offset, Derivative, Financial Liabilities	0	0
Net Amount Recognized, Derivative, Financial Liabilities	36,660	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, Derivative, Financial Liabilities		4,365
Gross Amount Offset, Derivative, Financial Liabilities		0
Net Amount Recognized, Derivative, Financial Liabilities		$ 4,365