Balance Sheet Offsetting - Financial Instruments Eligible for Offset Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	$ 11,978	$ 14,543
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	11,978	14,543
Gross Amount Recognized, Resell agreements, Financial assets	11,642	13,442
Gross Amount Offset, Resell agreements, Financial assets	0	0
Net Amount Recognized, Resell agreements, Financial assets	11,642	13,442
Gross Amount Recognized, Financial assets	23,620	27,985
Gross Amount Offset, Financial assets	0	0
Net Amount Recognized, Financial assets	23,620	27,985
Gross Amount Recognized, Derivatives, Financial Liabilities	57,551	40,198
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	57,551	40,198
Gross Amount Recognized, Repurchase agreements, Financial liabilities	685,036	883,947
Gross Amount Offset, Repurchase agreements, Financial liabilities	0	0
Net Amount Recognized, Repurchase agreements, Financial liabilities	685,036	883,947
Gross Amount Recognized, Financial liabilities	742,587	924,145
Gross Amount Offset, Financial liabilities	0	0
Net Amount Recognized, Financial Liabilities	742,587	924,145
Loan/lease interest rate swaps and caps [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	465	1,318
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	465	1,318
Commodity swaps and options [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	11,509	13,210
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	11,509	13,210
Gross Amount Recognized, Derivatives, Financial Liabilities	620	352
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	620	352
Foreign currency forward contracts [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	4	15
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	4	15
Gross Amount Recognized, Derivatives, Financial Liabilities	17	23
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	17	23
Loan/lease interest rate swaps [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Liabilities	56,914	39,823
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	$ 56,914	$ 39,823