Securities (Details 2) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Securities available for sale
Securities available for sale, Less than 12 months, Fair Value	$ 8,909	$ 8,919
Securities available for sale, Less than 12 months, Unrealized Losses	220	259
Securities available for sale, 12 months or more, Fair Value	1,316	2,289
Securities available for sale, 12 months or more, Unrealized Losses	28	32
Securities available for sale, Fair Value, Total	10,225	11,208
Securities available for sale, Unrealized Losses, Total	248	291
US Treasury Securities
Securities available for sale
Securities available for sale, Less than 12 months, Fair Value	2,270	2,257
Securities available for sale, Less than 12 months, Unrealized Losses	109	121
Securities available for sale, 12 months or more, Fair Value	0	0
Securities available for sale, 12 months or more, Unrealized Losses	0	0
Securities available for sale, Fair Value, Total	2,270	2,257
Securities available for sale, Unrealized Losses, Total	109	121
Residential mortgage-backed securities, U.S. government agency and government-sponsored agencies
Securities available for sale
Securities available for sale, Less than 12 months, Fair Value	5,567	5,501
Securities available for sale, Less than 12 months, Unrealized Losses	93	113
Securities available for sale, 12 months or more, Fair Value	606	667
Securities available for sale, 12 months or more, Unrealized Losses	8	9
Securities available for sale, Fair Value, Total	6,173	6,168
Securities available for sale, Unrealized Losses, Total	101	122
Residential mortgage-backed securities, Privately issued
Securities available for sale
Securities available for sale, Less than 12 months, Fair Value	249	249
Securities available for sale, Less than 12 months, Unrealized Losses	5	6
Securities available for sale, 12 months or more, Fair Value	26	29
Securities available for sale, 12 months or more, Unrealized Losses	1	1
Securities available for sale, Fair Value, Total	275	278
Securities available for sale, Unrealized Losses, Total	6	7
Privately issued - commercial mortgage-backed securities
Securities available for sale
Securities available for sale, Less than 12 months, Fair Value	371	415
Securities available for sale, Less than 12 months, Unrealized Losses	6	6
Securities available for sale, 12 months or more, Fair Value	11	11
Securities available for sale, 12 months or more, Unrealized Losses	0	0
Securities available for sale, Fair Value, Total	382	426
Securities available for sale, Unrealized Losses, Total	6	6
Collateralized loan obligations
Securities available for sale
Securities available for sale, Less than 12 months, Fair Value	168	75
Securities available for sale, Less than 12 months, Unrealized Losses	0	0
Securities available for sale, 12 months or more, Fair Value	129	1,077
Securities available for sale, 12 months or more, Unrealized Losses	1	5
Securities available for sale, Fair Value, Total	297	1,152
Securities available for sale, Unrealized Losses, Total	1	5
Asset-backed and other
Securities available for sale
Securities available for sale, Less than 12 months, Fair Value		0
Securities available for sale, Less than 12 months, Unrealized Losses		0
Securities available for sale, 12 months or more, Fair Value		1
Securities available for sale, 12 months or more, Unrealized Losses		0
Securities available for sale, Fair Value, Total		1
Securities available for sale, Unrealized Losses, Total		0
Asset Liability Management securities
Securities available for sale
Securities available for sale, Less than 12 months, Fair Value	8,625	8,497
Securities available for sale, Less than 12 months, Unrealized Losses	213	246
Securities available for sale, 12 months or more, Fair Value	772	1,785
Securities available for sale, 12 months or more, Unrealized Losses	10	15
Securities available for sale, Fair Value, Total	9,397	10,282
Securities available for sale, Unrealized Losses, Total	223	261
Other debt securities, Direct bank purchase bonds
Securities available for sale
Securities available for sale, Less than 12 months, Fair Value	193	386
Securities available for sale, Less than 12 months, Unrealized Losses	6	12
Securities available for sale, 12 months or more, Fair Value	539	499
Securities available for sale, 12 months or more, Unrealized Losses	18	17
Securities available for sale, Fair Value, Total	732	885
Securities available for sale, Unrealized Losses, Total	24	29
Other debt securities, Other
Securities available for sale
Securities available for sale, Less than 12 months, Fair Value	91	36
Securities available for sale, Less than 12 months, Unrealized Losses	1	1
Securities available for sale, 12 months or more, Fair Value	5	0
Securities available for sale, 12 months or more, Unrealized Losses	0	0
Securities available for sale, Fair Value, Total	96	36
Securities available for sale, Unrealized Losses, Total	$ 1	1
Equities
Securities available for sale
Securities available for sale, Less than 12 months, Fair Value		0
Securities available for sale, Less than 12 months, Unrealized Losses		0
Securities available for sale, 12 months or more, Fair Value		5
Securities available for sale, 12 months or more, Unrealized Losses		0
Securities available for sale, Fair Value, Total		5
Securities available for sale, Unrealized Losses, Total		$ 0

Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27290-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27337-111563

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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