Significant Accounting Policies (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
	Jan. 01, 2018	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred revenue and customer deposits		$ 229			$ 229		$ 205
Defined benefit plan, other cost (credit)		(5)		$ (1)	(15)	$ (5)
Adoption of new accounting guidance related to reclassification of certain tax effects	$ 45	$ 0	$ 45		$ 45
Deferred tax assets | Accounting Standards Update 2016-16
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment	(406)
Retained earnings | Accounting Standards Update 2016-16
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment	(406)
Retained earnings | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment	$ (9)