Goodwill and Other Intangible Assets (Schedule of Goodwill) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Goodwill Gross, Balance, beginning of period		$ 7,537	$ 7,916
Accumulated impairment losses, Balance, beginning of period		(2,814)	(1,395)
Goodwill, Balance, beginning of period		4,723	6,521
Goodwill acquired as part of acquisitions during current year		22	5
Consideration and purchase price allocation adjustments for prior year's acquisitions and other adjustments			(27)
Goodwill allocated to hospitals held for sale		(186)	(357)
Impairment of goodwill	$ (1,419)	0	(1,419)	$ (1,395)
Goodwill Gross, Balance, end of period	7,537	7,373	7,537	7,916
Accumulated impairment losses, Balance, end of period	(2,814)	(2,814)	(2,814)	(1,395)
Goodwill, Balance, end of period	$ 4,723	$ 4,559	$ 4,723	$ 6,521