Financial Instruments and Fair Value Measurements (Schedule of Equity Method Investments Summarized Information) (Details) - DigiCert - USD ($) $ in Millions	2 Months Ended	12 Months Ended
Dec. 31, 2017	Dec. 31, 2018
Equity Method Investment, Summarized Financial Information, Assets [Abstract]
Current assets	$ 261	$ 168
Long-term assets	1,810	1,641
Equity Method Investment, Summarized Financial Information, Liabilities [Abstract]
Current liabilities	246	331
Long-term liabilities	1,868	1,862
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Revenue	38	313
Gross profit	33	250
Net loss	$ (90)	$ (342)

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