Goodwill and Other Intangible Assets - Carrying Amounts of Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Changes in the Carrying Amount of Goodwill
Goodwill, beginning balance	$ 2,100.8	$ 1,972.6	$ 1,927.2
Acquisitions	179.5	128.2	45.4
Consolidation of joint venture formerly accounted for under the equity method of accounting	24.9
Goodwill, ending balance	2,305.2	2,100.8	1,972.6
Inpatient Rehabilitation
Schedule of Changes in the Carrying Amount of Goodwill
Goodwill, beginning balance	1,189.2	1,166.0	1,142.0
Acquisitions	4.8	23.2	24.0
Consolidation of joint venture formerly accounted for under the equity method of accounting	24.9
Goodwill, ending balance	1,218.9	1,189.2	1,166.0
Home Health and Hospice
Schedule of Changes in the Carrying Amount of Goodwill
Goodwill, beginning balance	911.6	806.6	785.2
Acquisitions	174.7	105.0	21.4
Consolidation of joint venture formerly accounted for under the equity method of accounting	0.0
Goodwill, ending balance	$ 1,086.3	$ 911.6	$ 806.6