Basis of Presentation and Significant Accounting Policies (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014 item	Dec. 31, 2013	Dec. 31, 2012
Business Description [Abstract]
Number of hospitals owned and leased by the Company	197
Number of stand alone rehabilitation or psychiatric hospitals	4
Number of licensed beds	30,137
Number of States in which Entity Operates	28
Cost of Revenue, Policy [Abstract]
Corporate Office Costs	$ 281,000,000	$ 181,000,000	$ 215,000,000
Stock-based compensation expense	54,000,000	38,000,000	41,000,000
Marketable Securities, Policy [Abstract]
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	0	2,000,000	3,000,000
Property and Equipment, Policy [Abstract]
Construction in Progress, Gross	350,000,000	232,000,000
Interest Costs Capitalized	10,000,000	11,000,000	24,000,000
Purchases of property and equipment accrued in accounts payable	190,000,000	142,000,000
Third-Party Reimbursement [Abstract]
Percentage of net operating revenues related to services rendered to patients covered by the Medicare and Medicaid programs	35.50%	34.50%	36.00%
Percentage of revenues from Medicare outlier payments included in amounts received from Medicare	0.41%	0.46%	0.47%
Reimbursement Settlement and Payment Included in Net Operating Revenues			105,000,000
Proceeds From Reimbursement Settlement Net of Related Legal Fees Paid			104,000,000
Unfavorable Adjustment Related To the Revised Supplemental Security Income Ratios Utilized for Calculating Medicare Disportionate Share Hospital Reimbursements			21,000,000
Amounts due to third party payors	147,000,000	61,000,000
Amounts due from third party payors	183,000,000	118,000,000
Net Operating Revenues, Policy [Abstract]
Provision for contractual allowance included in net operating revenues	84,400,000,000	52,600,000,000	48,500,000,000
Value of administrative and other discounts provided to self-pay patients included in contractual allowances	2,800,000,000	1,300,000,000	1,100,000,000
Value of charity care services at the Company's standard charges included in contractual allowances	550,000,000	681,000,000	669,000,000
Estimated cost incurred by Company to provide charity care services	84,000,000	116,000,000	120,000,000
Allowance for Doubtful Accounts, Policy [Abstract]
Percentage reserved for all non-self-pay payors accounts aging over 365 days from the date of discharge	100.00%
Number of days from the date of discharge over which all accounts are reserved 100%	365 days
Electronic Health Records Reimbursement, Policy [Abstract]
Electronic health records incentive reimbursement under HITECH	259,000,000	162,000,000	123,000,000
Electronic Health Records Incentive Reimbursement, Cash Received	253,000,000	203,000,000	141,000,000
Physician Income Guarantees, Policy [Abstract]
Finite-Lived Intangible Assets, Net	39,000,000	21,000,000
Concentration of Credit Risk, Policy [Abstract]
Accounts receivable, net of contractual allowances	3,409,000,000	2,323,000,000
Accounting for the Impairment or Disposal of Long-Lived Assets
Impairment of long-lived assets	17,000,000	12,000,000	10,000,000
Segment Reporting, Policy [Abstract]
Number of Operating Segments	2
Medicare [Member]
Concentration of Credit Risk, Policy [Abstract]
Accounts receivable, net of contractual allowances	453,000,000	360,000,000
Accounts receivable, net of contractual allowances, from Medicare as a percentage of consolidated net accounts receivable, before allowance for doubtful accounts	7.00%	8.00%
Electronic Health Records Incentive Reimbursements [Member]
Electronic Health Records Reimbursement, Policy [Abstract]
Deferred Revenue	81,000,000	90,000,000
Capitalized Internal Use Software, Significant System Conversions [Member] | Minimum [Member]
Other Assets, Policy [Abstract]
Finite-Lived Intangible Assets, Weighted-Average Useful Life	8 years
Capitalized Internal Use Software, Significant System Conversions [Member] | Maximum [Member]
Other Assets, Policy [Abstract]
Finite-Lived Intangible Assets, Weighted-Average Useful Life	10 years
Capitalized Internal Use Software, Except Significant System Conversions [Member]
Other Assets, Policy [Abstract]
Finite-Lived Intangible Assets, Weighted-Average Useful Life	3 years
Finite-Lived Intangible Assets, Except Capitalized Internal-Use Software [Member]
Other Assets, Policy [Abstract]
Finite-Lived Intangible Assets, Weighted-Average Useful Life	4 years
Physician recruitment contracts [Member]
Other Assets, Policy [Abstract]
Finite-Lived Intangible Assets, Weighted-Average Useful Life	3 years
Physician Income Guarantees, Policy [Abstract]
Physicians recruitment agreement period	1 year
Term of Physician Recruitment Contract	3 years
Finite-Lived Intangible Assets, Net	$ 48,000,000	$ 33,000,000
Land Improvements [Member] | Minimum [Member]
Property and Equipment, Policy [Abstract]
Property, Plant and Equipment, Useful Life	2 years
Land Improvements [Member] | Maximum [Member]
Property and Equipment, Policy [Abstract]
Property, Plant and Equipment, Useful Life	15 years
Land Improvements [Member] | Weighted Average [Member]
Property and Equipment, Policy [Abstract]
Property, Plant and Equipment, Useful Life	14 years
Building and Building Improvements [Member] | Minimum [Member]
Property and Equipment, Policy [Abstract]
Property, Plant and Equipment, Useful Life	5 years
Building and Building Improvements [Member] | Maximum [Member]
Property and Equipment, Policy [Abstract]
Property, Plant and Equipment, Useful Life	50 years
Building and Building Improvements [Member] | Weighted Average [Member]
Property and Equipment, Policy [Abstract]
Property, Plant and Equipment, Useful Life	24 years
Furniture and Fixtures [Member] | Minimum [Member]
Property and Equipment, Policy [Abstract]
Property, Plant and Equipment, Useful Life	4 years
Furniture and Fixtures [Member] | Maximum [Member]
Property and Equipment, Policy [Abstract]
Property, Plant and Equipment, Useful Life	18 years
Furniture and Fixtures [Member] | Weighted Average [Member]
Property and Equipment, Policy [Abstract]
Property, Plant and Equipment, Useful Life	8 years
Geographic Concentration Risk [Member] | Florida [Member] | Sales Revenue, Net [Member]
Business Description [Abstract]
Concentration Risk, Percentage	13.00%
Geographic Concentration Risk [Member] | Texas [Member] | Sales Revenue, Net [Member]
Business Description [Abstract]
Concentration Risk, Percentage	10.90%	15.00%	14.70%
Geographic Concentration Risk [Member] | Pennsylvania [Member] | Sales Revenue, Net [Member]
Business Description [Abstract]
Concentration Risk, Percentage	11.10%	13.10%	12.70%
Geographic Concentration Risk [Member] | Indiana [Member] | Sales Revenue, Net [Member]
Business Description [Abstract]
Concentration Risk, Percentage	7.60%	10.60%	10.70%