Business Combinations Business Combinations - Table 4 (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Apr. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Goodwill, Acquired During Period		$ 806.1	$ 593.1	$ 13.7
Payments to Acquire Businesses, Net of Cash Acquired		985.1	694.8	28.9
Inpatient Rehabilitation Hospital [Member]
Business Acquisition [Line Items]
Fair value of assets acquired		62.8	60.1	15.6
Goodwill, Acquired During Period	$ 0.7	0.7	34.6	13.7
Noncash or Part Noncash Acquisition, Value of Liabilities Assumed		(2.7)	(21.2)	(0.4)
Fair value of noncontrolling interest owned by joint venture partner		(4.2)	(18.3)	0.0
Business Combination, Step Acquisition, Equity Interest in Acquiree, Fair Value		0.0	(35.0)	0.0
Payments to Acquire Businesses, Net of Cash Acquired		$ 56.6	$ 20.2	$ 28.9