Goodwill and Other Intangible Assets - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 67	$ 79	$ 90
Projected amortization expense:
Projected amortization expense in 2019	61
Projected amortization expense in 2020	55
Projected amortization expense in 2021	50
Projected amortization expense in 2022	40
Projected amortization expense in 2023	$ 37