Balance Sheet Offsetting - Financial Instruments Derivative Assets Liabilities and Resell Agreements Net of Amount Not Offset (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	$ 96,708	$ 119,723
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(27,674)	(32,431)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(67,983)	(84,839)
Net Amount, Derivatives, Financial Assets	1,051	2,453
Net Amount Recognized, Resell agreements, Financial Assets	9,650	84,650
Gross Amounts Not Offset Financial Instruments, Resell Agreements	0	0
Gross Amounts Not Offset Collateral, Resell Agreements, Financial Assets	(9,650)	(84,650)
Net Amount, Financial Assets, Resell Agreements	0	0
Net Amount Recognized, Total Financial Assets	106,358	204,373
Gross Amounts Not Offset Collateral, Financial Assets	(77,633)	(169,489)
Net Amount, Financial Assets	1,051	2,453
Net Amount Recognized, Derivatives, Financial Liabilities	44,056	41,311
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(27,674)	(32,431)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	(16,382)	(8,580)
Net Amount, Derivatives, Financial Liabilities	0	300
Net Amount Recognized, Repurchase Agreements, Financial Liabilities	4,014,037	4,127,188
Gross Amounts Not Offset Financial Instruments, Repurchase Agreements, Financial Liabilities	0	0
Gross Amounts Not Offset Collateral, Repurchase Agreements, Financial Liabilities	(4,014,037)	(4,127,188)
Net Amount, Repurchase Agreements, Financial Liabilities	0	0
Net Amount Recognized, Total Financial Liabilities	4,058,093	4,168,499
Gross Amounts Not Offset Collateral, Financial Liabilities	(4,030,419)	(4,135,768)
Net Amount, Financial Liabilities	0	300
Counterparty H
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	37,881	36,551
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(9,014)	(8,870)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(28,867)	(27,170)
Net Amount, Derivatives, Financial Assets	0	511
Net Amount Recognized, Derivatives, Financial Liabilities	9,014	8,870
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(9,014)	(8,870)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	0	0
Net Amount, Derivatives, Financial Liabilities	0	0
Counterparty F
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	20,090	31,202
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(1,987)	(7,444)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(17,170)	(22,954)
Net Amount, Derivatives, Financial Assets	933	804
Net Amount Recognized, Derivatives, Financial Liabilities	1,987	7,444
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(1,987)	(7,444)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	0	0
Net Amount, Derivatives, Financial Liabilities	0	0
Counterparty B
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	22,591	23,829
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(4,525)	(5,151)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(18,066)	(18,472)
Net Amount, Derivatives, Financial Assets	0	206
Net Amount Recognized, Derivatives, Financial Liabilities	4,525	5,151
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(4,525)	(5,151)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	0	0
Net Amount, Derivatives, Financial Liabilities	0	0
Counterparty E
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	8,941	13,271
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(8,823)	(4,548)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	0	(8,723)
Net Amount, Derivatives, Financial Assets	118	0
Net Amount Recognized, Derivatives, Financial Liabilities	8,823	4,548
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(8,823)	(4,548)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	0	0
Net Amount, Derivatives, Financial Liabilities	0	0
Other counterparties
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	7,205	14,870
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(3,325)	(6,418)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(3,880)	(7,520)
Net Amount, Derivatives, Financial Assets	0	932
Net Amount Recognized, Derivatives, Financial Liabilities	19,707	15,298
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(3,325)	(6,418)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	(16,382)	(8,580)
Net Amount, Derivatives, Financial Liabilities	$ 0	$ 300