Employee Benefit Plans - Funded Status of Defined Benefit Pension Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Change in projected benefit obligations:
Interest cost	$ (20)	$ (9)
U.K. plan
Change in projected benefit obligations:
Plan benefit obligations, beginning balance	(672)	0
Acquired First Data plans (see Note 4)	0	(687)
Interest cost	(14)	(6)
Actuarial gain (loss)	(93)	28
Benefits paid	30	12
Foreign currency translation	(28)	(19)
Plan benefit obligations, ending balance	(777)	(672)
Change in fair value of plan assets:
Fair value of plan assets, beginning balance	860	0
Acquired First Data plans (see Note 4)	0	866
Actual return on plan assets	110	(19)
Company contribution	0	0
Benefits paid	(30)	(12)
Foreign currency translation	34	25
Fair value of plan assets, ending balance	974	860
Funded status of the plans	197	188
U.S. and other plans
Change in projected benefit obligations:
Plan benefit obligations, beginning balance	(225)	0
Acquired First Data plans (see Note 4)	0	(219)
Interest cost	(6)	(3)
Actuarial gain (loss)	(18)	(15)
Benefits paid	13	12
Foreign currency translation	(2)	0
Plan benefit obligations, ending balance	(238)	(225)
Change in fair value of plan assets:
Fair value of plan assets, beginning balance	167	0
Acquired First Data plans (see Note 4)	0	160
Actual return on plan assets	22	19
Company contribution	5	0
Benefits paid	(13)	(12)
Foreign currency translation	0	0
Fair value of plan assets, ending balance	181	167
Funded status of the plans	$ (57)	$ (58)