Business Combinations Business Combinations - Table 9 (Details) - USD ($) $ in Millions	2 Months Ended	3 Months Ended	7 Months Ended	9 Months Ended	10 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual			$ 27.2
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual			$ 4.0
Business Acquisition, Pro Forma Revenue							$ 2,799.8	$ 2,627.6
Business Acquisition, Pro Forma Net Income (Loss)							237.5	$ 311.3
Reliant [Member]
Business Acquisition [Line Items]
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual		$ 63.7
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual		$ 11.2
Inpatient Rehabilitation Hospital [Member]
Business Acquisition [Line Items]
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual				$ 54.7
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual				$ 1.7
CareSouth [Member]
Business Acquisition [Line Items]
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual	$ 19.2
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual	$ 2.5
Home Health and Hospice [Member]
Business Acquisition [Line Items]
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual					$ 17.8
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual					$ 1.2
2015 Acquisitions [Member]
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Revenue						$ 3,479.9	2,851.0
Business Acquisition, Pro Forma Net Income (Loss)						$ 234.0	$ 276.9