Balance Sheet Offsetting - Financial Instruments Eligible for Offset Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial assets	$ 12,745	$ 16,265
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	12,745	16,265
Gross Amount Recognized, Resell agreements, Financial assets	4,898	7,898
Gross Amount Offset, Resell agreements, Financial assets	0	0
Net Amount Recognized, Resell agreements, Financial assets	4,898	7,898
Gross Amount Recognized, Financial assets	17,643	24,163
Gross Amount Offset, Financial assets	0	0
Net Amount Recognized, Financial assets	17,643	24,163
Gross Amount Recognized, Derivatives, Financial liabilities	39,551	42,603
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	39,551	42,603
Gross Amount Recognized, Repurchase agreements, Financial liabilities	576,040	668,053
Gross Amount Offset, Repurchase agreements, Financial liabilities	0	0
Net Amount Recognized, Repurchase agreements, Financial liabilities	576,040	668,053
Gross Amount Recognized, Financial liabilities	615,591	710,656
Gross Amount Offset, Financial liabilities	0	0
Net Amount Recognized, Financial Liabilities	615,591	710,656
Loan/lease interest rate swaps and caps [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial assets	5,801	12,268
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	5,801	12,268
Commodity swaps and options [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial assets	6,121	3,907
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	6,121	3,907
Gross Amount Recognized, Derivatives, Financial liabilities	2,575	5,916
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	2,575	5,916
Foreign currency forward contracts [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial assets	823	90
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	823	90
Gross Amount Recognized, Derivatives, Financial liabilities	0	27
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	0	27
Loan/lease interest rate swaps [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial liabilities	36,976	36,660
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	$ 36,976	$ 36,660