Acquisitions (Preliminary Purchase Price Allocation) (Details) - USD ($) $ in Millions		Sep. 06, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill			$ 2,146	$ 2,096	$ 1,781
Nomor [Member]
Business Acquisition [Line Items]
Current assets	[1]	$ 11
Property and equipment		6
Goodwill		153
Identifiable intangible assets	[2]	66
Current liabilities	[3]	(20)
Long-term liabilities	[4]	(19)
Total purchase price		198
Deferred tax liabilities, tax differences in intangible assets		15
Cash Acquired from Acquisition		$ 9

[1] Primarily trade receivables and net of approximately $9 million of cash acquired.

[2] Primarily customer lists.

[3] Primarily advanced collections from customers.

[4] Includes $15 million of deferred tax liabilities recognized as a result of tax basis differences in intangible assets.