Securities (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Securities available for sale
Amortized Cost	$ 15,108	$ 14,378
Gross Unrealized Gains	65	54
Gross Unrealized Losses	248	291
Fair Value	14,925	14,141
U.S. Treasury securities
Securities available for sale
Amortized Cost	2,920	2,625
Gross Unrealized Gains	2	1
Gross Unrealized Losses	109	121
Fair Value	2,813	2,505
Residential mortgage-backed securities, U.S. government agency and government-sponsored agencies
Securities available for sale
Amortized Cost	7,474	6,814
Gross Unrealized Gains	5	3
Gross Unrealized Losses	101	122
Fair Value	7,378	6,695
Residential mortgage-backed securities, Privately issued
Securities available for sale
Amortized Cost	431	333
Gross Unrealized Gains	1	1
Gross Unrealized Losses	6	7
Fair Value	426	327
Privately issued - commercial mortgage-backed securities
Securities available for sale
Amortized Cost	664	666
Gross Unrealized Gains	5	4
Gross Unrealized Losses	6	6
Fair Value	663	664
Collateralized loan obligations
Securities available for sale
Amortized Cost	1,985	2,219
Gross Unrealized Gains	13	4
Gross Unrealized Losses	1	5
Fair Value	1,997	2,218
Other Asset Liability Management Securities
Securities available for sale
Amortized Cost	7	7
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	7	7
Asset Liability Management securities
Securities available for sale
Amortized Cost	13,481	12,664
Gross Unrealized Gains	26	13
Gross Unrealized Losses	223	261
Fair Value	13,284	12,416
Other debt securities, Direct bank purchase bonds
Securities available for sale
Amortized Cost	1,528	1,601
Gross Unrealized Gains	39	41
Gross Unrealized Losses	24	29
Fair Value	1,543	1,613
Other debt securities, Other
Securities available for sale
Amortized Cost	94	108
Gross Unrealized Gains	0	0
Gross Unrealized Losses	1	1
Fair Value	93	107
Equities
Securities available for sale
Amortized Cost	5	5
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 5	$ 5

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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