Goodwill and Other Intangible Assets (Schedule of Goodwill) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Goodwill [Roll Forward]
Goodwill Gross, Balance, beginning of period	$ 7,537
Accumulated impairment losses, Balance, beginning of period	(2,814)
Goodwill, Balance, beginning of period	4,723
Goodwill acquired as part of acquisitions during current year	6
Goodwill allocated to hospitals held for sale	(25)	$ (192)
Goodwill Gross, Balance, end of period	7,518
Accumulated impairment losses, Balance, end of period	(2,814)
Goodwill, Balance, end of period	$ 4,704