Acquisitions and Strategic Investments Strategic Investments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 24, 2018	Nov. 01, 2017
Schedule of Equity Method Investments [Line Items]
Other Nonoperating Income (Expense)	$ (124)	$ (37)	$ (83)
Equity Method Investments	209	265
Cost Method Investments	81	20
Available-for-sale Securities	15	20
Notes Receivable From Portfolio Companies	47	42
Investments	353	$ 347
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	212
Subsequent Event [Member]
Schedule of Equity Method Investments [Line Items]
Total consideration for share purchase				$ 90
Closing payment				325
Potential payments based on acheiving certain milestones				$ 125
Investee Company [Member]
Schedule of Equity Method Investments [Line Items]
potential up-front cash payment					$ 145
potential contingent payments to acquire investee					$ 130
investment impairment [Member]
Schedule of Equity Method Investments [Line Items]
Other Nonoperating Income (Expense)	$ (72)