Balance Sheet Offsetting - Financial Instruments Derivative Assets Liabilities and Resell Agreements Net of Amount Not Offset (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	$ 129,313	$ 118,994
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(47,959)	(62,528)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(80,310)	(55,968)
Net Amount, Derivatives, Financial Assets	1,044	498
Net Amount Recognized, Resell agreements, Financial Assets	84,650	87,150
Gross Amounts Not Offset Financial Instruments, Resell Agreements	0	0
Gross Amounts Not Offset Collateral, Resell Agreements, Financial Assets	(84,650)	(87,150)
Net Amount, Financial Assets, Resell Agreements	0	0
Net Amount Recognized, Total Financial Assets	213,963	206,144
Gross Amounts Not Offset Collateral, Financial Assets	(164,960)	(143,118)
Net Amount, Financial Assets	1,044	498
Net Amount Recognized, Derivatives, Financial Liabilities	55,909	73,829
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(47,959)	(62,528)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	(7,950)	(9,330)
Net Amount, Derivatives, Financial Liabilities	0	1,971
Net Amount Recognized, Repurchase Agreements, Financial Liabilities	3,722,245	4,660,641
Gross Amounts Not Offset Financial Instruments, Repurchase Agreements, Financial Liabilities	0	0
Gross Amounts Not Offset Collateral, Repurchase Agreements, Financial Liabilities	(3,722,245)	(4,660,641)
Net Amount, Repurchase Agreements, Financial Liabilities	0	0
Net Amount Recognized, Total Financial Liabilities	3,778,154	4,734,470
Gross Amounts Not Offset Collateral, Financial Liabilities	(3,730,195)	(4,669,971)
Net Amount, Financial Liabilities	0	1,971
Counterparty B
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	29,882	39,370
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(8,795)	(24,500)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(21,087)	(14,870)
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities	8,795	24,500
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(8,795)	(24,500)
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	19,272	14,430
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(597)	(47)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(18,675)	(14,131)
Net Amount, Derivatives, Financial Assets	0	252
Net Amount Recognized, Derivatives, Financial Liabilities	597	47
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(597)	(47)
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	19,028	17,297
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(19,028)	(17,297)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	0	0
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities	26,978	27,747
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(19,028)	(17,297)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	(7,950)	(8,479)
Net Amount, Derivatives, Financial Liabilities	0	1,971
Counterparty G
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	9,907	10,660
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	0	0
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(9,907)	(10,660)
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities		0
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities		0
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities		0
Net Amount, Derivatives, Financial Liabilities		0
Other counterparties
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	51,224	37,237
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(19,539)	(20,684)
Gross Amount Not Offset Collateral, Derivatives, Financial Assets	(30,641)	(16,307)
Net Amount, Derivatives, Financial Assets	1,044	246
Net Amount Recognized, Derivatives, Financial Liabilities	19,539	21,535
Gross Amounts Not Offset Financial Instruments, Total Derivatives, Financial Liabilities	(19,539)	(20,684)
Gross Amounts Not Offset Collateral, Derivatives, Financial Liabilities	0	(851)
Net Amount, Derivatives, Financial Liabilities	$ 0	$ 0