Business Combinations Business Combinations - Table 3 (Details) - USD ($) $ in Millions	Dec. 31, 2015	Oct. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Business Acquisition [Line Items]
Property and equipment, net		$ 220.6
Goodwill	$ 1,890.1		$ 1,084.0	$ 456.9	$ 437.3
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net		771.4
Inpatient Rehabilitation Hospital [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets	10.1
Property and equipment, net	42.7
Goodwill	0.7
Total assets acquired	63.4
Total liabilities assumed	2.7
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net	60.7
Noncompete Agreements [Member]
Business Acquisition [Line Items]
Identifiable intangible assets, Finite life		9.7
Noncompete Agreements [Member] | Inpatient Rehabilitation Hospital [Member]
Business Acquisition [Line Items]
Identifiable intangible assets, Finite life	0.1
Trade Names [Member]
Business Acquisition [Line Items]
Identifiable intangible assets, Finite life		8.9
Trade Names [Member] | Inpatient Rehabilitation Hospital [Member]
Business Acquisition [Line Items]
Identifiable intangible assets, Finite life	0.8
Certificate of Need [Member]
Business Acquisition [Line Items]
Identifiable intangible assets, Finite life		36.6
Certificate of Need [Member] | Inpatient Rehabilitation Hospital [Member]
Business Acquisition [Line Items]
Identifiable intangible assets, Finite life	8.8
License [Member]
Business Acquisition [Line Items]
Identifiable intangible assets, Finite life		$ 11.4
License [Member] | Inpatient Rehabilitation Hospital [Member]
Business Acquisition [Line Items]
Identifiable intangible assets, Finite life	$ 0.2