Goodwill and Other Intangible Assets - Changes in Goodwill and Other Intangible Assets (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018 USD ($)
Goodwill and Other Intangible Assets [Roll Forward]
Amortizing Intangible Assets, Beginning Balance	$ 355
Amortizing Intangible Assets, Amortization expense	51
Amortizing Intangible Assets, Ending Balance	359
Goodwill, Beginning Balance	3,815
Goodwill, Other Increase (Decrease)	(2)
Goodwill, Ending Balance	4,083
Other Non-Amortizing Intangible Assets, Beginning Balance	1,254
Other Non-Amortizing Intangible Assets, Ending Balance	2,649
Centaur Holdings, LLC [Member]
Goodwill and Other Intangible Assets [Roll Forward]
Finite-lived Intangible Assets Acquired	55	[1]
Goodwill, Acquired During Period	270	[1]
Indefinite-lived Intangible Assets Acquired	1,390	[1]
Other Intangible Assets [Member]
Goodwill and Other Intangible Assets [Roll Forward]
Amortizing Intangible Assets, Amortization expense	0
Other Intangible Assets [Member]
Goodwill and Other Intangible Assets [Roll Forward]
Other Non-Amortizing Intangible Assets, Beginning Balance	253
Indefinite-lived Intangible Assets	5
Other Non-Amortizing Intangible Assets, Ending Balance	$ 253

[1] (1) See Note 4 for further details relating to the acquisition of Centaur.