Credit Risk and Interest Rate Risk (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Secured financing agreements
Gross Amounts of Recognized  Assets (Liabilities)	$ (2,686,522)	$ (3,434,765)
Gross Amounts Offset in the Consolidated Statements of Financial Position	0	0
Repurchase agreements outstanding	(2,686,522)	(3,434,765)
Gross amounts not offset with financial assets (liabilities) in the consolidated statements of financial position, financial instruments	3,898,631	4,699,722
Gross amounts not offset with financial assets (liabilities) in the consolidated statements of financial position, cash collateral (received) pledged	15,304	33,415
Net Amount	1,227,413	1,298,373
Derivative Asset
Net Amounts Offset in the Consolidated Statements of Financial Position	6,328	4,096
Derivative Liability
Net Amounts Offset in the Consolidated Statements of Financial Position	0	0
Total Repurchase Agreements and Swaptions
Gross Amounts of Recognized  Assets (Liabilities)	(2,651,851)
Gross Amounts Offset in the Consolidated Statements of Financial Position	(28,343)
Net Amounts Offset in the Consolidated Statements of Financial Position	(2,680,194)
Gross amounts not offset with financial assets (liabilities) in the consolidated statements of financial position, financial instruments	3,898,631
Gross amounts not offset with financial assets (liabilities) in the consolidated statements of financial position, cash collateral (received) pledged	15,304
Net Amount	1,233,741
Total Derivative Liabilities, Securities Sold and Securities Loaned
Gross Amounts of Recognized  Assets (Liabilities)		(3,430,046)
Gross Amounts Offset in the Consolidated Statements of Financial Position		(623)
Net Amounts Offset in the Consolidated Statements of Financial Position		(3,430,669)
Gross amounts not offset with financial assets (liabilities) in the consolidated statements of financial position, financial instruments		4,699,722
Gross amounts not offset with financial assets (liabilities) in the consolidated statements of financial position, cash collateral (received) pledged		74,271
Net Amount		1,343,326
Future
Derivative Asset
Net Amounts Offset in the Consolidated Statements of Financial Position	0
Derivative Liability
Net Amounts Offset in the Consolidated Statements of Financial Position	0
Interest Rate Swaps
Derivative Asset
Gross Amounts of Recognized  Assets (Liabilities)	17,890	3,716
Gross Amounts Offset in the Consolidated Statements of Financial Position	(11,783)	0
Net Amounts Offset in the Consolidated Statements of Financial Position	6,107	3,716
Gross amounts not offset with financial assets (liabilities) in the consolidated statements of financial position, financial instruments	0	0
Gross amounts not offset with financial assets (liabilities) in the consolidated statements of financial position, cash collateral (received) pledged	0	13,179
Net Amount	6,107	16,895
Derivative Liability
Gross Amounts of Recognized  Assets (Liabilities)		(14,074)
Gross Amounts Offset in the Consolidated Statements of Financial Position		14,074
Net Amounts Offset in the Consolidated Statements of Financial Position	0	0
Gross amounts not offset with financial assets (liabilities) in the consolidated statements of financial position, financial instruments		0
Gross amounts not offset with financial assets (liabilities) in the consolidated statements of financial position, cash collateral (received) pledged		27,678
Net Amount		27,678
Swaptions
Derivative Asset
Gross Amounts of Recognized  Assets (Liabilities)	16,781	15,077
Gross Amounts Offset in the Consolidated Statements of Financial Position	(16,560)	(14,697)
Net Amounts Offset in the Consolidated Statements of Financial Position	221	380
Gross amounts not offset with financial assets (liabilities) in the consolidated statements of financial position, financial instruments	0	0
Gross amounts not offset with financial assets (liabilities) in the consolidated statements of financial position, cash collateral (received) pledged	0	0
Net Amount	221	380
Derivative Liability
Net Amounts Offset in the Consolidated Statements of Financial Position	$ 0	$ 0