Basis of Presentation and Summary of Significant Accounting Policies Cash and Cash equivalents (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Accounting Policies [Abstract]
Cash and Cash Equivalents, at Carrying Value	$ 1,605	$ 509	$ 388
Restricted Cash	9	7	21
Funds held for clients included in other current assets	26	32	45
Cash included in settlement processing assets included in other current assets	18	15	9
Cash, Cash Equivalents, Restricted Cash and Restricted Cash at end of period	$ 1,658	$ 563	$ 463