Fair Value of Financial Assets and Liabilities - Nonrecurring (Details) - Fair Value, Measurements, Nonrecurring [Member] - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trade Receivables Held-for-sale, Amount	$ 15	$ 757
Total Liabilities held for sale	40	169
Long-term debt	1,512	1,979
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trade Receivables Held-for-sale, Amount	15	757
Total Liabilities held for sale	40	169
Long-term debt	$ 1,463	$ 2,070