Balance Sheet Offsetting - Financial Instruments Eligible for Offset Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	$ 10,657	$ 27,849
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	10,657	27,849
Gross Amount Recognized, Resell agreements, Financial assets	10,193	11,642
Gross Amount Offset, Resell agreements, Financial assets	0	0
Net Amount Recognized, Resell agreements, Financial assets	10,193	11,642
Gross Amount Recognized, Financial assets	20,850	39,491
Gross Amount Offset, Financial assets	0	0
Net Amount Recognized, Financial assets	20,850	39,491
Gross Amount Recognized, Derivatives, Financial Liabilities	24,155	11,185
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	24,155	11,185
Gross Amount Recognized, Repurchase agreements, Financial liabilities	1,308,257	1,360,298
Gross Amount Offset, Repurchase agreements, Financial liabilities	0	0
Net Amount Recognized, Repurchase agreements, Financial liabilities	1,308,257	1,360,298
Gross Amount Recognized, Financial liabilities	1,332,412	1,371,483
Gross Amount Offset, Financial liabilities	0	0
Net Amount Recognized, Financial Liabilities	1,332,412	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	916	3,100
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	916	3,100
Commodity swaps and options [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	9,741	24,749
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	9,741	24,749
Gross Amount Recognized, Derivatives, Financial Liabilities	4,060	1,918
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	4,060	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	14	147
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	14	147
Loan/lease interest rate swaps [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Liabilities	20,081	9,120
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	$ 20,081	$ 9,120

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