Fair Value Measurements - Fair Values - Financial Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Fair Value
Financial assets
Current assets	$ 4	$ 3
Other noncurrent assets	29	76
Total financial assets	33	79
Financial liabilities
Other current liabilities	75	37
Long-term debt, including current portion	6,018	5,469
Deferred credits and other liabilities	108	93
Total financial liabilities	6,201	5,599
Carrying Amount
Financial assets
Current assets	4	3
Other noncurrent assets	35	81
Total financial assets	39	84
Financial liabilities
Other current liabilities	103	58
Long-term debt, including current portion	5,529	5,528
Deferred credits and other liabilities	96	88
Total financial liabilities	$ 5,728	$ 5,674