Acquisitions (Preliminary Purchase Price Allocation) (Details) - USD ($) $ in Millions		Sep. 06, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill			$ 2,279	$ 1,956	$ 1,780
Nomor [Member]
Business Acquisition [Line Items]
Property and equipment		$ 6
Goodwill		127
Identifiable intangible assets	[1]	94
Current liabilities	[2]	(18)
Long-term liabilities	[3]	(22)
Total purchase price		198
Deferred tax liabilities, tax differences in intangible assets		20
Cash Acquired from Acquisition		$ 9

[1] Primarily customer lists.

[2] Primarily advanced collections from customers.

[3] Includes $20 million of deferred tax liabilities recognized as a result of tax basis differences in intangible assets.