Basis of Presentation and Significant Accounting Policies (Schedule of Operating Revenue) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Net operating revenues	$ 3,689	$ 4,486
Medicare [Member]
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Net operating revenues	1,033	1,234
Medicaid [Member]
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Net operating revenues	459	587
Managed Care And Other Third Party Payors [Member]
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Net operating revenues	2,117	2,528
Self Pay Revenue [Member]
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Net operating revenues	$ 80	$ 137