Derivative Instruments (Offsetting Assets and Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Derivatives Assets
Gross Amounts of Recognized Financial Instruments	$ 5,781,434	$ 7,086,534
Gross Amounts Offset in the Consolidated Statement of Financial Position	(5,579,018)	(6,818,009)
Net Amounts Presented in the Consolidated Statement of Financial Position	202,416	268,525
Financial Instruments/Collateral	0	0
Net Amount	202,416	268,525
Securities Purchased under Agreements to Resell
Gross Amounts of Recognized Financial Instruments	300,000	185,000
Gross Amounts Offset in the Consolidated Statement of Financial Position	0	0
Net Amounts Presented in the Consolidated Statement of Financial Position	300,000	185,000
Financial Instruments/Collateral	(300,000)	(185,000)
Net Amount	0	0
Total Assets
Gross Amounts of Recognized Financial Instruments	6,081,434	7,271,534
Gross Amounts Offset in the Consolidated Statement of Financial Position	(5,579,018)	(6,818,009)
Net Amounts Presented in the Consolidated Statement of Financial Position	502,416	453,525
Financial Instruments/Collateral	(300,000)	(185,000)
Net Amount	202,416	268,525
Derivatives Liabilities
Gross Amounts of Recognized Financial Instruments	12,045,224	12,573,983
Gross Amounts Offset in the Consolidated Statement of Financial Position	(11,987,555)	(12,568,082)
Net Amounts Presented in the Consolidated Statement of Financial Position	57,668	5,901
Financial Instruments/Collateral	(57,668)	(5,901)
Net Amount	0	0
Securities Sold under Agreements to Repurchase
Gross Amounts of Recognized Financial Instruments	0	0
Gross Amounts Offset in the Consolidated Statement of Financial Position	0	0
Net Amounts Presented in the Consolidated Statement of Financial Position	0	0
Financial Instruments/Collateral	0	0
Net Amount	0	0
Total Liabilities
Gross Amounts of Recognized Financial Instruments	12,045,224	12,573,983
Gross Amounts Offset in the Consolidated Statement of Financial Position	(11,987,555)	(12,568,082)
Net Amounts Presented in the Consolidated Statement of Financial Position	57,668	5,901
Financial Instruments/Collateral	(57,668)	(5,901)
Net Amount	$ 0	$ 0