Basis of Presentation and Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
Net Operating Revenues, Policy [Abstract]
Value of charity care services at the Company's standard charges included in contractual allowances	$ 115	$ 112	$ 229	$ 228
Estimated cost incurred by Company to provide charity care services	14	$ 15	28	29
Patient accounts receivable, net of allowance for doubtful accounts	2,407		2,407			$ 2,384
Third-Party Reimbursement [Abstract]
Amounts due to third party payors	133		133			156
Amounts due from third party payors	$ 149		149			$ 153
Accounting for the Impairment or Disposal of Long-Lived Assets
Impairment and (gain) loss on sale of businesses, net			202	330
Goodwill allocated to hospital disposal group held for sale			$ 77	$ 357
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Net Operating Revenues, Policy [Abstract]
Patient accounts receivable, net of allowance for doubtful accounts					$ 3,900
ASU 2016-01 [Member]
New Accounting Pronouncements, Policy [Abstract]
Accumulated other comprehensive loss reclassified to accumulated deficit					6
ASU 2018-02 [Member]
New Accounting Pronouncements, Policy [Abstract]
Accumulated other comprehensive loss reclassified to accumulated deficit					$ 6