Basis of Presentation and Summary of Significant Accounting Policies Cash and Cash equivalents (Details) - USD ($) $ in Millions	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Cash and Cash Equivalents, at Carrying Value	$ 1,681	$ 1,214	$ 509	$ 388	$ 335	$ 414	$ 464
Restricted Cash	9	7	7	21	10	9	12
Funds held for clients included in other current assets	28	44	32	45	46	64	46
Cash included in settlement processing assets included in other current assets	21	8	15	9	10	9	10
Cash, Cash Equivalents, Restricted Cash and Restricted Cash at end of period	$ 1,739	$ 1,273	$ 563	$ 463	$ 401	$ 496	$ 532