Derivatives - Interest Rate Swap Contracts, Swaptions and Futures Contracts (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Derivative [Line Items]
Notional Amount	$ 7,410,000,000	$ 7,210,000,000
Weighted Average Remaining Term (Months)	75 months	77 months
Weighted Average Rate	0.66%	0.63%
Notional amount, forward settling	$ 950,000,000
Fed Funds Effective Rate Overnight Index Swap Rate
Derivative [Line Items]
Notional Amount	6,007,000,000	$ 6,007,000,000
Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Derivative [Line Items]
Notional Amount	$ 1,403,000,000	$ 1,203,000,000
Less than 3 years
Derivative [Line Items]
Derivative, remaining maturity	3 years	3 years
Notional Amount	$ 1,593,000,000	$ 1,593,000,000
Weighted Average Remaining Term (Months)	12 months	15 months
Weighted Average Rate	0.08%	0.08%
Greater than or equal to 3 years and less than 5 years
Derivative [Line Items]
Notional Amount	$ 865,000,000	$ 708,000,000
Weighted Average Remaining Term (Months)	54 months	57 months
Weighted Average Rate	0.24%	0.24%
Greater than or equal to 5 years and less than 7 years
Derivative [Line Items]
Notional Amount	$ 650,000,000	$ 707,000,000
Weighted Average Remaining Term (Months)	65 months	64 months
Weighted Average Rate	1.05%	0.88%
Greater than or equal to 7 years
Derivative [Line Items]
Notional Amount	$ 4,302,000,000	$ 4,202,000,000
Weighted Average Remaining Term (Months)	105 months	107 months
Weighted Average Rate	0.90%	0.87%
Minimum | Greater than or equal to 3 years and less than 5 years
Derivative [Line Items]
Derivative, remaining maturity	3 years	3 years
Minimum | Greater than or equal to 5 years and less than 7 years
Derivative [Line Items]
Derivative, remaining maturity	5 years	5 years
Maximum | Greater than or equal to 3 years and less than 5 years
Derivative [Line Items]
Derivative, remaining maturity	5 years	5 years
Maximum | Greater than or equal to 5 years and less than 7 years
Derivative [Line Items]
Derivative, remaining maturity	7 years	7 years
Maximum | Greater than or equal to 7 years
Derivative [Line Items]
Derivative, remaining maturity	7 years	7 years