Fair Value Measurements - Gains (Loss) and Interest Expense on Interest Rate Swap Contracts (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
(Loss) gain recorded in accumulated other comprehensive income (loss), net of tax	$ (5)	$ (1)
Interest rate swap
Derivative Instruments, Gain (Loss) [Line Items]
(Loss) gain recorded in accumulated other comprehensive income (loss), net of tax	(5)	2
Interest expense recorded related to interest rate swap contracts	$ 0	$ 1