Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
HTM securities, fair value	$ 22,837	$ 16,546
Preferred stock, par value per share (in usd per share)	$ 5	$ 5
Preferred stock, liquidation preference per share (in usd per share)	25,000	25,000
Common stock, par value per share (in usd per share)	$ 5	$ 5

Face amount or stated value per share of common stock.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
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Fair value of investments in debt securities classified as held-to-maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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The price per share at which the preferred stock of an entity that has priority over common stock in the distribution of dividends and in the event of liquidation of the entity is redeemed or may be called at. The redemption features of this preferred stock are solely within the control of the issuer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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