Asset Quality - Summary of Allowance for Loan and Lease Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	$ 882	$ 824	$ 823
Charge-offs	(328)	(289)	(238)
Recoveries	102	67	74
Provision for loan and lease losses from continuing operations	229	266	166
Ending balance	893	882	824
Continuing Operations [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	858	796	794
Charge-offs	(302)	(261)	(203)
Recoveries	94	56	61
Net loans and leases charged off	(208)	(205)	(142)
Provision for loan and lease losses from continuing operations	227	267	145
Foreign currency translation adjustment	0	0	1
Ending balance	877	858	796
Discontinued Operations [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	24	28	29
Charge-offs	(26)	(28)	(35)
Recoveries	8	11	13
Ending balance	$ 16	$ 24	$ 28