Goodwill and Other Intangible Assets - Changes In The Carrying Amount Of Other Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Finite-lived Intangible Assets [Roll Forward]
Beginning balance	$ 1,613	$ 1,750	$ 1,750
Acquisitions	0		16
Divestitures	0		(11)
Amortization	(50)	(52)	(214)
Foreign currency translation and other, net	15		72
Ending balance	1,578		1,613
Investment Servicing
Finite-lived Intangible Assets [Roll Forward]
Beginning balance	1,432	1,539	1,539
Acquisitions	0		16
Divestitures	0		(11)
Amortization	(43)		(183)
Foreign currency translation and other, net	15		71
Ending balance	1,404		1,432
Investment Management
Finite-lived Intangible Assets [Roll Forward]
Beginning balance	181	$ 211	211
Acquisitions	0		0
Divestitures	0		0
Amortization	(7)		(31)
Foreign currency translation and other, net	0		1
Ending balance	$ 174		$ 181