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, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Operating revenues (net of contractual allowances and discounts)	$ 5,614	$ 5,508	$ 11,260	$ 10,383
Medicare [Member]
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Operating revenues (net of contractual allowances and discounts)	1,383	1,367	2,782	2,628
Medicaid [Member]
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Operating revenues (net of contractual allowances and discounts)	616	585	1,202	1,044
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)	2,947	2,859	5,892	5,309
Self-Pay [Member]
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Operating revenues (net of contractual allowances and discounts)	$ 668	$ 697	$ 1,384	$ 1,402