Acquisitions and Divestitures (Divestitures Narrative) (Details) $ in Millions		3 Months Ended
	May 01, 2017 USD ($) item	Mar. 31, 2018 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Divestiture of Businesses, Net of Cash Divested		$ 11
AllianceHealth Pryor [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Date		May 01, 2017
Number of licensed beds | item	52
Proceeds from Divestiture of Businesses, Net of Cash Divested	$ 1