Loans and ACL - Allowance for Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Provision for credit losses	$ 155	$ 150
Commercial \| Commercial and industrial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
ACL, beginning balance	546	522
Charge-Offs	(17)	(23)
Recoveries	6	8
Provision for credit losses	13	15
ACL, ending balance	548	522
Commercial \| CRE
Financing Receivable, Allowance for Credit Losses [Roll Forward]
ACL, beginning balance	190	160
Charge-Offs	(8)	(6)
Recoveries	1	2
Provision for credit losses	13	19
ACL, ending balance	196	175
Commercial \| Lease financing
Financing Receivable, Allowance for Credit Losses [Roll Forward]
ACL, beginning balance	11	9
Charge-Offs	(1)	(1)
Recoveries	0	0
Provision for credit losses	1	2
ACL, ending balance	11	10
Retail \| Residential mortgage
Financing Receivable, Allowance for Credit Losses [Roll Forward]
ACL, beginning balance	232	209
Charge-Offs	(5)	(4)
Recoveries	1	0
Provision for credit losses	(3)	11
ACL, ending balance	225	216
Retail \| Direct
Financing Receivable, Allowance for Credit Losses [Roll Forward]
ACL, beginning balance	97	106
Charge-Offs	(18)	(19)
Recoveries	6	6
Provision for credit losses	11	6
ACL, ending balance	96	99
Retail \| Indirect
Financing Receivable, Allowance for Credit Losses [Roll Forward]
ACL, beginning balance	356	348
Charge-Offs	(109)	(107)
Recoveries	17	15
Provision for credit losses	94	91
ACL, ending balance	358	347
Revolving credit
Financing Receivable, Allowance for Credit Losses [Roll Forward]
ACL, beginning balance	117	108
Charge-Offs	(26)	(21)
Recoveries	6	5
Provision for credit losses	22	12
ACL, ending balance	119	104
PCI
Financing Receivable, Allowance for Credit Losses [Roll Forward]
ACL, beginning balance	9	28
Charge-Offs	0	0
Recoveries	0	0
Provision for credit losses	(1)	(3)
ACL, ending balance	8	25
ALLL
Financing Receivable, Allowance for Credit Losses [Roll Forward]
ACL, beginning balance	1,558	1,490
Charge-Offs	(184)	(181)
Recoveries	37	36
Provision for credit losses	150	153
ACL, ending balance	1,561	1,498
RUFC
Financing Receivable, Allowance for Credit Losses [Roll Forward]
ACL, beginning balance	93	119
Charge-Offs	0	0
Recoveries	0	0
Provision for credit losses	5	(3)
ACL, ending balance	98	116
ACL
Financing Receivable, Allowance for Credit Losses [Roll Forward]
ACL, beginning balance	1,651	1,609
Charge-Offs	(184)	(181)
Recoveries	37	36
Provision for credit losses	155	150
ACL, ending balance	$ 1,659	$ 1,614

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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- Definition

Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

+ References

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- Definition

A valuation allowance for financing receivables that are expected to be uncollectible.

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+ References

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- Definition

Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.11)
-URI http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

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