Balance Sheet Offsetting - Financial Instruments Derivative Assets Liabilities and Resell Agreements Net of Amount Not Offset (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	$ 127,209	$ 23,339
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(89,314)	(23,339)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(33,803)	0
Net Amount, Derivatives, Financial Assets	4,092	0
Net Amount Recognized, Resell agreements, Financial Assets	12,150	7,903
Gross Amounts Not Offset Financial Instruments, Resell Agreements	0	0
Gross Amounts Not Offset Collateral, Resell Agreements, Financial Assets	(12,150)	(7,903)
Net Amount, Financial Assets, Resell Agreements	0	0
Net Amount Recognized, Total Financial Assets	139,359	31,242
Gross Amounts Not Offset Collateral, Financial Assets	(45,953)	(7,903)
Net Amount, Financial Assets	4,092	0
Net Amount Recognized, Derivatives, Financial Liabilities	97,033	114,019
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(89,314)	(23,339)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	(7,716)	(90,573)
Net Amount, Derivatives, Financial Liabilities	3	107
Net Amount Recognized, Repurchase Agreements, Financial Liabilities	2,082,739	2,740,799
Gross Amounts Not Offset Financial Instruments, Repurchase Agreements, Financial Liabilities	0	0
Gross Amounts Not Offset Collateral, Repurchase Agreements, Financial Liabilities	(2,082,739)	(2,740,799)
Net Amount, Repurchase Agreements, Financial Liabilities	0	0
Net Amount Recognized, Total Financial Liabilities	2,179,772	2,854,818
Gross Amounts Not Offset Collateral, Financial Liabilities	(2,090,455)	(2,831,372)
Net Amount, Financial Liabilities	3	107
Counterparty A [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	47	6
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(47)	(6)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	0	0
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities	1,081	3,870
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(47)	(6)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	(1,031)	(3,864)
Net Amount, Derivatives, Financial Liabilities	3	0
Counterparty B [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	44,271	7,655
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(35,853)	(7,655)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(6,063)	0
Net Amount, Derivatives, Financial Assets	2,355	0
Net Amount Recognized, Derivatives, Financial Liabilities	35,853	28,130
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(35,853)	(7,655)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	0	(20,475)
Net Amount, Derivatives, Financial Liabilities	0	0
Counterparty C [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	407
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(251)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	0
Net Amount, Derivatives, Financial Assets	156
Net Amount Recognized, Derivatives, Financial Liabilities	251	9
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(251)	0
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	0	(9)
Net Amount, Derivatives, Financial Liabilities	0	0
Other Counterparties [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	82,484	15,678
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(53,163)	(15,678)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(27,740)	0
Net Amount, Derivatives, Financial Assets	1,581	0
Net Amount Recognized, Derivatives, Financial Liabilities	59,848	82,010
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(53,163)	(15,678)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	(6,685)	(66,225)
Net Amount, Derivatives, Financial Liabilities	$ 0	$ 107