Offsetting Assets and Liabilities - Offsetting of Derivative Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Derivatives:
Gross Amounts of Recognized Assets (Liabilities)		$ (2,079)
Gross Amounts Offset in the Balance Sheets		0
Net Amounts of Assets (Liabilities) Presented in the Balance Sheets		(2,079)
Financial Instruments		642
Cash Collateral (Received) Pledged		1,297
Net Amount		(140)
Repurchase Agreements:
Gross Amounts of Recognized Assets (Liabilities)	$ (4,987,006)	(4,234,823)
Gross Amounts Offset in the Balance Sheets	0	0
Net Amounts of Assets (Liabilities) Presented in the Balance Sheets	(4,987,006)	(4,234,823)
Financial Instruments	4,987,006	4,234,823
Cash Collateral (Received) Pledged	0	0
Net Amount	0	0
Gross Amounts of Recognized Assets (Liabilities)	(4,987,006)	(4,236,902)
Gross Amounts Offset in the Balance Sheets	0	0
Net Amounts of Assets (Liabilities) Presented in the Balance Sheets	(4,987,006)	(4,236,902)
Financial Instruments	4,987,006	4,235,465
Cash Collateral (Received) Pledged	0	1,297
Net Amount	0	(140)
Fair value of securities pledged under repurchase agreements, excluding cash collateral	5,200,000	4,400,000
Cash collateral pledged on derivatives	185,800	104,800
Cash collateral pledged on interest rate swaps	$ 185,800	103,200
Cash
Repurchase Agreements:
Cash collateral received		$ 4,900