Goodwill and Other Intangible Assets - Changes in Carrying Value of Goodwill and Other Intangible Assets (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019 USD ($)
Amortizing Intangible Assets
Balance as of beginning of period	$ 342
Amortization	(53)
Impairments	0
Other	0
Transferred to assets held for sale	(1)
Balance as of end of period	288
Goodwill
Balance as of beginning of period	4,044
Impairments	0
Other	(1)
Transferred to assets held for sale	(5)
Balance as of end of period	4,038
Other
Balance as of beginning of period	2,635
Impairments	(50)
Other	(3)
Transferred to assets held for sale	(20)
Balance as of end of period	$ 2,562