Accrued Expenses and Other Liabilities - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accrued Liabilities and Other Liabilities [Abstract]
Benefit (charge) within operating expense	$ (1)	$ 9	$ (9)