Investment Securities - Contractual Maturities and Weighted-Average Yields of Securities (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Securities available for sale
Due in 1 year or less	$ 6,144
Due after 1 year through 5 years	9,001
Due after 5 years through 10 years	5,434
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	74,682
Securities available for sale	95,261	$ 100,445
Amortized cost of securities available for sale
Due in 1 year or less	6,140
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost	8,965
Due after 5 years through 10 years	5,342
Due > 10 Years	74,424
Amortized Cost	$ 94,871
Weighted average yield for securities available for sale
Due in 1 Year or Less	0.31%
Due > 1 Year through 5 Years	0.90%
Due > 5 Years through 10 Years	1.86%
Due > 10 Years	1.73%
Total weighted average yield	1.57%
U.S. Treasury securities
Securities available for sale
Due in 1 year or less	$ 5,098
Due after 1 year through 5 years	4,344
Due after 5 years through 10 years	0
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	0
Securities available for sale	9,442	9,318
RMBS, Agency
Securities available for sale
Due in 1 year or less	0
Due after 1 year through 5 years	132
Due after 5 years through 10 years	1,124
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	71,364
Securities available for sale	72,620	75,466
RMBS, Non-agency
Securities available for sale
Due in 1 year or less	0
Due after 1 year through 5 years	0
Due after 5 years through 10 years	0
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	996
Securities available for sale	996	1,237
RMBS
Securities available for sale
Due in 1 year or less	0
Due after 1 year through 5 years	132
Due after 5 years through 10 years	1,124
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	72,360
Securities available for sale	$ 73,616	$ 76,703
Weighted average yield for securities available for sale
Weighted-average expected life	5 years 4 months 24 days	5 years 4 months 24 days
CMBS, Agency
Securities available for sale
Due in 1 year or less	$ 630
Due after 1 year through 5 years	2,427
Due after 5 years through 10 years	3,990
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	2,322
Securities available for sale	9,369	$ 11,735
Other securities
Securities available for sale
Due in 1 year or less	416
Due after 1 year through 5 years	2,098
Due after 5 years through 10 years	320
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	0
Securities available for sale	$ 2,834	$ 2,689

Available-for-sale Securities, Expected Debt Maturities, Amortized Cost Basis, Rolling Maturity

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Debt Maturities, Available-for-Sale, Weighted Average Expected Life

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 30
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Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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