Basis of Presentation - Recently Adopted Accounting Pronoucements (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($)	Jul. 01, 2017 USD ($)	Jun. 30, 2018 USD ($) segment	Jul. 01, 2017 USD ($)	Dec. 31, 2017 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of segments | segment			2
Retained Earnings | Accounting Standards Update 2016-16
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting pronouncement					$ (30)
Restatement Adjustment | Accounting Standards Update 2017-07 | Other income (expense)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net periodic benefit excluding service cost	$ 20	$ 4	$ 40	$ 1