Business Combinations Allocation of Purchase Price (Details) $ in Millions	9 Months Ended
	Sep. 30, 2021 USD ($)
Business Acquisition [Line Items]
Cash	$ 47
Trade accounts receivable	73
Property and equipment and other assets	23
Operating lease assets, net	43
Non-deductible goodwill	237
Current liabilities	71
Noncurrent liabilities	106
Purchase price, inclusive of contingent consideration	778
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Tax-Deductible Goodwill	229
Linium
Business Acquisition [Line Items]
Cash	0
Trade accounts receivable	5
Property and equipment and other assets	1
Operating lease assets, net	0
Non-deductible goodwill	0
Current liabilities	2
Noncurrent liabilities	0
Purchase price, inclusive of contingent consideration	85
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Tax-Deductible Goodwill	57
Magenic
Business Acquisition [Line Items]
Cash	13
Trade accounts receivable	17
Property and equipment and other assets	4
Operating lease assets, net	10
Non-deductible goodwill	10
Current liabilities	30
Noncurrent liabilities	7
Purchase price, inclusive of contingent consideration	246
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Tax-Deductible Goodwill	138
ESG Mobility
Business Acquisition [Line Items]
Cash	28
Trade accounts receivable	24
Property and equipment and other assets	8
Operating lease assets, net	27
Non-deductible goodwill	31
Current liabilities	20
Noncurrent liabilities	65
Purchase price, inclusive of contingent consideration	134
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Tax-Deductible Goodwill	24
Servian
Business Acquisition [Line Items]
Cash	4
Trade accounts receivable	15
Property and equipment and other assets	6
Operating lease assets, net	5
Non-deductible goodwill	180
Current liabilities	12
Noncurrent liabilities	29
Purchase price, inclusive of contingent consideration	248
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Tax-Deductible Goodwill	0
Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Cash	2
Trade accounts receivable	12
Property and equipment and other assets	4
Operating lease assets, net	1
Non-deductible goodwill	16
Current liabilities	7
Noncurrent liabilities	5
Purchase price, inclusive of contingent consideration	65
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Tax-Deductible Goodwill	10
Customer Relationships [Member]
Business Acquisition [Line Items]
Intangible assets acquired	$ 300
Weighted Average Useful Life	10 years
Customer Relationships [Member] | Linium
Business Acquisition [Line Items]
Intangible assets acquired	$ 24
Customer Relationships [Member] | Magenic
Business Acquisition [Line Items]
Intangible assets acquired	90
Customer Relationships [Member] | ESG Mobility
Business Acquisition [Line Items]
Intangible assets acquired	77
Customer Relationships [Member] | Servian
Business Acquisition [Line Items]
Intangible assets acquired	77
Customer Relationships [Member] | Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Intangible assets acquired	32
Other Intangible Assets [Member]
Business Acquisition [Line Items]
Intangible assets acquired	$ 3
Weighted Average Useful Life	3 years 9 months 18 days
Other Intangible Assets [Member] | Linium
Business Acquisition [Line Items]
Intangible assets acquired	$ 0
Other Intangible Assets [Member] | Magenic
Business Acquisition [Line Items]
Intangible assets acquired	1
Other Intangible Assets [Member] | ESG Mobility
Business Acquisition [Line Items]
Intangible assets acquired	0
Other Intangible Assets [Member] | Servian
Business Acquisition [Line Items]
Intangible assets acquired	2
Other Intangible Assets [Member] | Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Intangible assets acquired	$ 0