Business Combinations Allocation of Purchase Price (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Cash	$ 13
Trade accounts receivable	63
Property and equipment and other assets	24
Operating lease assets, net	18
Non-deductible goodwill	435
Goodwill	4,391	$ 3,979
Current liabilities	51
Noncurrent liabilities	22
Purchase price, inclusive of contingent consideration(1)	544
Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Cash	8
Trade accounts receivable	22
Property and equipment and other assets	19
Operating lease assets, net	12
Non-deductible goodwill	108
Current liabilities	21
Noncurrent liabilities	18
Purchase price, inclusive of contingent consideration(1)	144
Collaborative Solutions [Member]
Business Acquisition [Line Items]
Cash	5
Trade accounts receivable	41
Property and equipment and other assets	5
Operating lease assets, net	6
Non-deductible goodwill	327
Current liabilities	30
Noncurrent liabilities	4
Purchase price, inclusive of contingent consideration(1)	400
Customer Relationships [Member]
Business Acquisition [Line Items]
Intangible assets acquired	$ 54
Weighted Average Useful Life	9 years 2 months 12 days
Customer Relationships [Member] | Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Intangible assets acquired	$ 12
Customer Relationships [Member] | Collaborative Solutions [Member]
Business Acquisition [Line Items]
Intangible assets acquired	42
Other Intangible Assets [Member]
Business Acquisition [Line Items]
Intangible assets acquired	$ 10
Weighted Average Useful Life	6 years 6 months
Other Intangible Assets [Member] | Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Intangible assets acquired	$ 2
Other Intangible Assets [Member] | Collaborative Solutions [Member]
Business Acquisition [Line Items]
Intangible assets acquired	$ 8