Long-Term Debt - Components of Long-Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Finance lease liabilities	$ 7	$ 11
Total long-term debt	12,042	13,709
Real Estate Loans and securities pledged	604	607
Senior Medium-Term Notes Due Through 2021
Debt Instrument [Line Items]
Senior medium-term notes	$ 2,820	$ 3,962
Long-term debt weighted average interest rate (as a percent)	3.2213%	3.7025%
3.136% Subordinated notes due 2028
Debt Instrument [Line Items]
Debt instrument interest rate (as a percent)	2.075%
Subordinated long-term notes	$ 162	$ 162
6.875% Subordinated Notes Due 2029
Debt Instrument [Line Items]
Debt instrument interest rate (as a percent)	6.875%
Subordinated long-term notes	$ 107	115
7.750% Subordinated Notes Due 2029
Debt Instrument [Line Items]
Debt instrument interest rate (as a percent)	7.75%
Subordinated long-term notes	$ 139	149
7.25% Subordinated notes due 2021
Debt Instrument [Line Items]
Debt instrument interest rate (as a percent)	7.25%
Subordinated long-term notes	$ 0	$ 311
Long-term debt weighted average interest rate (as a percent)		7.25%
Other Subordinated Notes
Debt Instrument [Line Items]
Subordinated long-term notes	$ 75	$ 74
Long-term debt weighted average interest rate (as a percent)	1.68%	1.72%
Senior Medium-Term Notes Due Through 2039
Debt Instrument [Line Items]
Senior medium-term notes	$ 6,582	$ 6,718
Long-term debt weighted average interest rate (as a percent)	2.116%	2.516%
3.18% Senior Remarketable Notes Due 2027
Debt Instrument [Line Items]
Debt instrument interest rate (as a percent)	3.18%
Subordinated long-term notes	$ 242	$ 232
Long-term debt weighted average interest rate (as a percent)	3.18%	3.18%
3.40% Subordinated notes due 2026
Debt Instrument [Line Items]
Debt instrument interest rate (as a percent)	3.40%
Subordinated long-term notes	$ 602	$ 625
6.95% Subordinated notes due 2028
Debt Instrument [Line Items]
Debt instrument interest rate (as a percent)	6.95%
Subordinated long-term notes	$ 299	299
3.90% Subordinated notes due 2029
Debt Instrument [Line Items]
Debt instrument interest rate (as a percent)	3.90%
Subordinated long-term notes	$ 376	398
Secured Borrowing Due Through 2025
Debt Instrument [Line Items]
Secured borrowing due through 2025	$ 13	$ 19
Long-term debt weighted average interest rate (as a percent)	4.445%	4.445%
Federal Home Loan Bank Advances Due Through 2038
Debt Instrument [Line Items]
Federal Home Loan Bank advances due through 2038	$ 604	$ 608
Long-term debt weighted average interest rate (as a percent)	1.12%	1.15%
Investment Fund Financing Due Through 2052
Debt Instrument [Line Items]
Investment Fund Financing due through 2052	$ 10	$ 21
Long-term debt weighted average interest rate (as a percent)	1.34%	1.77%
Key Government Finance Incorporated Other Long Term Debt ASR
Debt Instrument [Line Items]
Key Govt Finance, Inc. Other Long Term Debt-ASR	$ 3	$ 4
Obligations Under Capital Lease Due Through 2032
Debt Instrument [Line Items]
Finance lease liabilities	8	12
Key
Debt Instrument [Line Items]
Total long-term debt	3,303	4,773
Subsidiaries
Debt Instrument [Line Items]
Total long-term debt	$ 8,739	$ 8,936

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Amount of long-term debt classified as other.

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