Debt Securities (Schedule Of Cost And Estimated Fair Value Of Securities Available For Sale And Securities Held To Maturity By Contractual Maturity) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Debt Securities held to maturity, amortized cost	$ 913	$ 1,143
Debt Securities held to maturity, estimated fair value	950	1,215
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost	325
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value	328
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Amortized Cost	1,289
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value	1,304
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Amortized Cost	855
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value	860
Debt Securities, Available-for-sale, Allocated and Single Maturity Date, Maturity, after 10 Years, Amortized Cost	117
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value	117
Debt Securities, Available-for-sale, Amortized Cost	28,263	26,092
Debt securities available for sale	28,481	27,154
Residential Agency [Member]
Debt Securities held to maturity, amortized cost	370	554
Debt Securities held to maturity, estimated fair value	377	569
Debt Securities, Available-for-sale, Amortized Cost	18,873	18,455
Debt securities available for sale	18,962	19,076
Residential Non-Agency [Member]
Debt Securities, Available-for-sale, Amortized Cost	1	1
Debt securities available for sale	1	1
Commercial Agency [Member]
Debt Securities held to maturity, amortized cost	543	589
Debt Securities held to maturity, estimated fair value	573	646
Debt Securities, Available-for-sale, Amortized Cost	6,271	5,659
Debt securities available for sale	6,373	5,999
Commercial Non Agency [Member]
Debt Securities, Available-for-sale, Amortized Cost	532	571
Debt securities available for sale	$ 536	$ 586

Held To Maturity Amortized Cost Basis before transfer from available for sale

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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).

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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), with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount 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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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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