Basis of Presentation and Significant Accounting Policies (Narrative) (Details) $ in Millions	3 Months Ended		6 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2017 USD ($) state item	Dec. 31, 2015 USD ($)	Jun. 30, 2016 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2017 USD ($) segment state item	Dec. 31, 2016 USD ($) segment	Dec. 31, 2015 USD ($)
Business Description [Abstract]
Number of hospitals owned and leased by the Company | item	125				125
Number of stand alone rehabilitation or psychiatric hospitals | item	2				2
Number of licensed beds | item	20,850				20,850
Number of States in which Entity Operates | state	19				19
Cost of Revenue, Policy [Abstract]
Corporate Office Costs					$ 189	$ 197	$ 266
Stock-based compensation expense					24	46	59
Marketable Securities, Policy [Abstract]
Change in Fair Value of Available for Sale Securities, Activity during the year, net of tax					8	(11)	(5)
Property and Equipment, Policy [Abstract]
Construction in Progress, Gross	$ 222				222	227
Interest Costs Capitalized					11	9	16
Purchases of property and equipment accrued in accounts payable					166	115
Non-cash investing activity through capital leases					31	179	$ 50
Goodwill, Policy [Abstract]
Impairment of goodwill			$ 1,400	$ 1,395	$ 1,419	$ 1,395
Third-Party Reimbursement [Abstract]
Percentage of net operating revenues related to services rendered to patients covered by the Medicare and Medicaid programs					33.10%	34.40%	35.30%
Percentage of revenues from Medicare outlier payments included in amounts received from Medicare					0.33%	0.38%	0.28%
Amounts due to third party payors	156				$ 156	$ 99
Amounts due from third party payors	153				153	186
Net Operating Revenues, Policy [Abstract]
Provision for contractual allowance included in net operating revenues					93,600	98,200	$ 95,300
Value of administrative and other discounts provided to self-pay patients included in contractual allowances					3,600	3,200	3,000
Value of charity care services at the Company's standard charges included in contractual allowances					482	487	453
Estimated cost incurred by Company to provide charity care services					62	64	64
Allowance for doubtful patient accounts	3,870				3,870	3,773
Patient accounts receivable, net of allowance for doubtful accounts	2,384				2,384	3,176
Allowance for Doubtful Accounts, Policy [Abstract]
Health Care Organization, Patient Service Revenue Provision for Bad Debts					$ 3,045	2,837	3,127
Number of Hospitals Sold | item					30
Electronic Health Records Reimbursement, Policy [Abstract]
Electronic health records incentive reimbursement under HITECH					$ 28	70	160
Electronic Health Records Incentive Reimbursement, Cash Received					41	123	75
Physician Income Guarantees, Policy [Abstract]
Finite-Lived Intangible Assets, Net	10				10	14
Concentration of Credit Risk, Policy [Abstract]
Accounts receivable, net of contractual allowances	2,384				2,384	3,176
Accounting for the Impairment or Disposal of Long-Lived Assets
Goodwill allocated to hospital disposal group held for sale					357	365
Impairment and (gain) loss on sale of businesses, net					$ 2,123	$ 1,919	68
Segment Reporting, Policy [Abstract]
Number of Operating Segments | segment					1	2
New Accounting Pronouncements, Policy [Abstract]
Reclassification of debt issuance costs	191				$ 191
Provision for (benefit from) income taxes					(449)	$ (104)	$ 116
ASU 2014-09 [Member]
Net Operating Revenues, Policy [Abstract]
Provision for contractual allowance included in net operating revenues					197
Allowance for doubtful patient accounts	394				394
Patient accounts receivable, net of allowance for doubtful accounts	(591)				(591)
Concentration of Credit Risk, Policy [Abstract]
Accounts receivable, net of contractual allowances	(591)				(591)
ASU 2016-09 [Member]
New Accounting Pronouncements, Policy [Abstract]
Provision for (benefit from) income taxes					16
Additional Reserve [Member]
Allowance for Doubtful Accounts, Policy [Abstract]
Health Care Organization, Patient Service Revenue Provision for Bad Debts		$ 169
Medicare [Member]
Net Operating Revenues, Policy [Abstract]
Patient accounts receivable, net of allowance for doubtful accounts	220				220	402
Concentration of Credit Risk, Policy [Abstract]
Accounts receivable, net of contractual allowances	$ 220				$ 220	$ 402
Accounts receivable, net of contractual allowances, from Medicare as a percentage of consolidated net accounts receivable, before allowance for doubtful accounts	4.00%				4.00%	6.00%
Electronic Health Records Incentive Reimbursements [Member]
Electronic Health Records Reimbursement, Policy [Abstract]
Deferred Revenue	$ 0				$ 0
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					6 years
Physician Recruitment Contracts [Member]
Physician Income Guarantees, Policy [Abstract]
Physicians recruitment agreement period					1 year
Term of Physician Recruitment Contract					3 years
Finite-Lived Intangible Assets, Net	29				$ 29	$ 37
Land Improvements [Member] | Minimum [Member]
Property and Equipment, Policy [Abstract]
Property, Plant and Equipment, Useful Life					3 years
Land Improvements [Member] | Maximum [Member]
Property and Equipment, Policy [Abstract]
Property, Plant and Equipment, Useful Life					20 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					40 years
Furniture and Fixtures [Member] | Minimum [Member]
Property and Equipment, Policy [Abstract]
Property, Plant and Equipment, Useful Life					3 years
Furniture and Fixtures [Member] | Maximum [Member]
Property and Equipment, Policy [Abstract]
Property, Plant and Equipment, Useful Life					18 years
Certain Facility [Member]
Property and Equipment, Policy [Abstract]
Non-cash investing activity through capital leases					$ 31
Geographic Concentration Risk [Member] | Florida [Member] | Sales Revenue Net [Member]
Business Description [Abstract]
Concentration Risk, Percentage					14.80%	14.10%	13.60%
Geographic Concentration Risk [Member] | Texas [Member] | Sales Revenue Net [Member]
Business Description [Abstract]
Concentration Risk, Percentage					12.10%	11.40%	11.10%
Geographic Concentration Risk [Member] | Pennsylvania [Member] | Sales Revenue Net [Member]
Business Description [Abstract]
Concentration Risk, Percentage					9.20%	11.20%	10.60%
Geographic Concentration Risk [Member] | Indiana [Member] | Sales Revenue Net [Member]
Business Description [Abstract]
Concentration Risk, Percentage					9.90%	8.60%	7.30%
Certain Hospitals [Member]
Accounting for the Impairment or Disposal of Long-Lived Assets
Impairment of long-lived assets held for sale	$ 341				$ 388	$ 326
Impairment of long-lived assets marketed for sale					$ 7	270
Impairment charge recorded on the sale or closure of hospitals						19
Impairment and (gain) loss on sale of businesses, net						$ 615
Home Care [Member]
Segment Reporting, Policy [Abstract]
Percentage of Ownership Interest Sold						80.00%