Balance Sheet Offsetting - Financial Instruments Eligible for Offset Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	$ 15,250	$ 27,849
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	15,250	27,849
Gross Amount Recognized, Resell agreements, Financial assets	11,299	11,642
Gross Amount Offset, Resell agreements, Financial assets	0	0
Net Amount Recognized, Resell agreements, Financial assets	11,299	11,642
Gross Amount Recognized, Financial assets	26,549	39,491
Gross Amount Offset, Financial assets	0	0
Net Amount Recognized, Financial assets	26,549	39,491
Gross Amount Recognized, Derivatives, Financial Liabilities	26,012	11,185
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	26,012	11,185
Gross Amount Recognized, Repurchase agreements, Financial liabilities	1,187,355	1,360,298
Gross Amount Offset, Repurchase agreements, Financial liabilities	0	0
Net Amount Recognized, Repurchase agreements, Financial liabilities	1,187,355	1,360,298
Gross Amount Recognized, Financial liabilities	1,213,367	1,371,483
Gross Amount Offset, Financial liabilities	0	0
Net Amount Recognized, Financial Liabilities	1,213,367	1,371,483
Loan/lease interest rate swaps and caps [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	313	3,100
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	313	3,100
Commodity swaps and options [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	14,937	24,749
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	14,937	24,749
Gross Amount Recognized, Derivatives, Financial Liabilities	1,554	1,918
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	1,554	1,918
Foreign currency forward contracts [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	0	0
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	0	0
Gross Amount Recognized, Derivatives, Financial Liabilities	11	147
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	11	147
Loan/lease interest rate swaps [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Liabilities	24,447	9,120
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	$ 24,447	$ 9,120

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