Basis of Presentation ASUs Implemented (Details) - Accounting Standards Update 2014-09 [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Jan. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 55	$ 177
Other Current Liabilities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]	59
Other Noncurrent Liabilities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]	206
Other Noncurrent Assets [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]	12
Deferred Income Tax Charge [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]	41