Fair Value Measurements Fair Value Tables of Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Millions		Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		$ 58	$ 72
Derivative Liability		17	21
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents and Restricted Cash Equivalents	[1]	2,750	3,551
Marketable Securities		18	34
Assets at Fair Value		2,826	3,657
Long-term Debt, Fair Value		6,865	6,100
Liabilities at Fair Value		6,882	6,121
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Exchange Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	[2]	58	72
Derivative Liability	[2]	$ 17	$ 21

[1] Time deposits included in cash and cash equivalents and money market funds included in other current assets in the interim Condensed Consolidated Balance Sheets are held at amortized cost, which approximates fair value.

[2] See Note 16 for the classification of derivatives in the interim Condensed Consolidated Balance Sheets.