Fair Value Measurements - Book Values and Fair Values of Financial Instruments (Detail) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Book Values
Fair Value And Carrying Value By Balance Sheet Grouping [Line Items]
Short-term debt	$ 0	$ 2
Current maturities of long-term debt and finance lease obligations	2	2
Long-term debt and finance lease obligations	5,063	3,481
Fair values
Fair Value And Carrying Value By Balance Sheet Grouping [Line Items]
Short-term debt	0	2
Current maturities of long-term debt and finance lease obligations	2	2
Long-term debt and finance lease obligations	$ 5,466	$ 3,469