Investment Securities (Gains (Losses) on Sales of Securities Available for Sale) (Details) - USD ($)	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Investment Securities Disclosure [Abstract]
Proceeds	$ 4,490,000,000	$ 3,222,000,000
Gross Gains	37,000,000	14,000,000
Gross Losses	(38,000,000)	(16,000,000)
Net Losses	$ (1,000,000)	(2,000,000)
Tax Benefit		$ (1,000,000)

Income tax expense related to the gains (losses) of the sale of Available for sale securities.

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- Definition

Investment Securities Disclosure

+ References

No definition available.

+ Details

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- Definition

This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563

+ Details

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- Definition

This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

+ References

+ Details

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- Definition

This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

+ References

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- Definition

The net cash paid (received) associated with the acquisition or disposal of all investments, including securities and other assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3098-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3095-108585

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