Pension, Postretirement and Savings Plans Narrative (Details) £ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2020 GBP (£)
Total expense related to defined contribution plans	$ 150	$ 127	$ 98
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Projected benefit obligation increase (decrease)	$ 73	$ 93
Healthcare cost trend rate assumed for next year	7.00%	6.00%		7.00%
Ultimate trend rate	5.00%	5.00%		5.00%
Year that the rate reaches the ultimate trend rate	8 years	2 years
Plan assets at fair value	$ 542	$ 437
2021	19
2022	12
2023	14
2024	15
2025	15
2026 - 2030	77
Cash and cash equivalents
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value	59	16
Mutual funds
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value	387	346
Insurance contracts
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value	96	75
Other Postretirement Benefits Plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation, beginning	64	57
Service cost	1	1	1
Interest cost	2	2	2
Actuarial (gain) loss	7	9
Benefits paid	(4)	(5)
Transfers in	0	0
Foreign currency translation	0	0
Benefit Obligation, ending	70	64	57
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Actual (loss) gain on plan assets	0	0
Employer contributions	4	5
Benefits paid	(4)	(5)
Transfers in	0	0
Foreign currency translation	0	0
Funded status at end of year	(70)	(64)
Noncurrent assets	0	0
Other liabilities, short-term	(4)	(3)
Other liabilities, long-term	(66)	(61)
Total amounts recognized on the consolidated balance sheet	(70)	(64)
Net actuarial (gain) loss	9	2
Prior service credit	(4)	(5)
Balance at end of year	$ 5	$ (3)
Weighted-average assumptions used to determine end of year benefit obligations, Discount Rate	2.50%	3.25%		2.50%
Weighted-average assumptions used to determine end of year benefit obligations, rate of compensation increase	3.00%	3.00%		3.00%
Expected return on plan assets	$ 0	$ 0	0
Amortization of actuarial loss	0	0	0
Amortization of prior service credit	(1)	(1)	(2)
Net periodic benefit cost	2	2	1
Current year actuarial loss (gain)	7	9	(2)
Current year prior service credit	0	0	0
Amortization of prior service credit	1	1	2
Total other comprehensive loss (income)	8	10	0
Total net periodic benefit cost and other comprehensive loss (income)	$ 10	$ 12	$ 1
Weighted-average assumptions used to determine end of year net periodic benefit, Discount rate	3.25%	4.25%	3.50%
Weighted-average assumptions used to determine end of year net periodic benefit, Rate of compensation increase	3.00%	3.00%	3.00%
Plan assets at fair value	$ 0	$ 0	$ 0
2021	4
2022	4
2023	4
2024	4
2025	4
2026 - 2030	20
Pension Plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation, beginning	531	438
Service cost	13	11	9
Interest cost	9	13	12
Actuarial (gain) loss	43	73
Benefits paid	(18)	(15)
Transfers in	3	2
Foreign currency translation	23	9
Benefit Obligation, ending	604	531	438
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Actual (loss) gain on plan assets	56	79
Employer contributions	34	32
Benefits paid	(18)	(15)
Transfers in	5	2
Foreign currency translation	22	10
Funded status at end of year	13	(13)
Noncurrent assets	28	0
Other liabilities, short-term	0	0
Other liabilities, long-term	(15)	(13)
Total amounts recognized on the consolidated balance sheet	13	(13)
Net actuarial (gain) loss	12	7
Prior service credit	1	1
Balance at end of year	13	8
Projected benefit obligation	604	531
Accumulated benefit obligation	601	524
Fair value of plan assets	617	518
Expected return on plan assets	(18)	(18)	(20)
Amortization of actuarial loss	0	1	0
Amortization of prior service credit	0	0	0
Net periodic benefit cost	4	7	1
Current year actuarial loss (gain)	5	12	17
Current year prior service credit	0	0	1
Amortization of prior service credit	0	0	0
Total other comprehensive loss (income)	5	12	18
Total net periodic benefit cost and other comprehensive loss (income)	9	$ 19	19
Plan assets at fair value	$ 617		$ 410
Pension Plan | Foreign Plan [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Weighted-average assumptions used to determine end of year benefit obligations, Discount Rate	0.70%	0.70%		0.70%
Weighted-average assumptions used to determine end of year benefit obligations, rate of compensation increase	1.50%	1.50%		1.50%
Weighted-average assumptions used to determine end of year net periodic benefit, Discount rate	0.70%	1.80%	1.80%
Weighted-average assumptions used to determine end of year net periodic benefit, Expected return on plan assets	1.60%	2.10%	3.00%
Weighted-average assumptions used to determine end of year net periodic benefit, Rate of compensation increase	1.50%	1.50%	2.60%
Fair Value, Inputs, Level 1
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value	$ 329	$ 169
Fair Value, Inputs, Level 1 | Cash and cash equivalents
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value	59	16
Fair Value, Inputs, Level 1 | Mutual funds
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value	270	153
Fair Value, Inputs, Level 1 | Insurance contracts
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value	0	0
Fair Value, Inputs, Level 2
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value	213	268
Fair Value, Inputs, Level 2 | Cash and cash equivalents
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value	0	0
Fair Value, Inputs, Level 2 | Mutual funds
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value	117	193
Fair Value, Inputs, Level 2 | Insurance contracts
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value	96	75
Fair Value, Inputs, Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value	0	0
Fair Value, Inputs, Level 3 | Cash and cash equivalents
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value	0	0
Fair Value, Inputs, Level 3 | Mutual funds
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value	0	0
Fair Value, Inputs, Level 3 | Insurance contracts
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value	0	0
Investments at Net Asset Value (NAV)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Total Plan Assets	617	$ 518
Vocalink Plan
Expected future employer contributions	$ 20			£ 15
Vocalink Plan | Non-government fixed income
Plan assets, target allocation (percent)	35.00%			35.00%
Vocalink Plan | Cash and cash equivalents
Plan assets, target allocation (percent)	12.00%			12.00%
Vocalink Plan | Government and agency securities
Plan assets, target allocation (percent)	23.00%			23.00%
Vocalink Plan | Other
Plan assets, target allocation (percent)	8.00%			8.00%
Vocalink Plan | Equity Securities
Plan assets, target allocation (percent)	22.00%			22.00%
Vocalink Plan | Pension Plan
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Weighted-average assumptions used to determine end of year benefit obligations, Discount Rate	1.55%	2.00%		1.55%
Weighted-average assumptions used to determine end of year benefit obligations, rate of compensation increase	2.75%	2.50%		2.75%
Weighted-average assumptions used to determine end of year net periodic benefit, Discount rate	1.55%	2.00%	2.80%
Weighted-average assumptions used to determine end of year net periodic benefit, Expected return on plan assets	3.20%	3.75%	4.75%
Weighted-average assumptions used to determine end of year net periodic benefit, Rate of compensation increase	2.75%	2.50%	3.85%
Pension Plans with Benefit Obligations in Excess of Plan Assets | Pension Plan
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Projected benefit obligation	$ 112
Accumulated benefit obligation	111
Fair value of plan assets	97
Mutual funds | Investments at Net Asset Value (NAV)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Alternative Investment	$ 75	$ 81