Basis of Presentation and Significant Accounting Policies (Schedule of Operating Revenue, Net of Contractual Allowances and Discounts (But Before the Provision for Bad Debts)) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Operating revenues (net of contractual allowances and discounts)	$ 5,290	$ 5,614	$ 11,044	$ 11,260
Medicare [Member]
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Operating revenues (net of contractual allowances and discounts)	1,265	1,383	2,696	2,782
Medicaid [Member]
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Operating revenues (net of contractual allowances and discounts)	553	616	1,145	1,202
Managed Care And Other Third Party Payors [Member]
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Operating revenues (net of contractual allowances and discounts)	2,816	2,947	5,839	5,892
Self-Pay [Member]
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Operating revenues (net of contractual allowances and discounts)	$ 656	$ 668	$ 1,364	$ 1,384