Segment Reporting - Selected Financial Information of Reportable Segments (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Net operating revenues	$ 1,184.4	$ 1,161.6	$ 1,135.0	$ 1,124.0	$ 1,096.0	$ 1,067.6	$ 1,067.7	$ 1,046.0	$ 4,605.0	$ 4,277.3	$ 3,913.9
Operating expenses:
Salaries and benefits									2,573.0	2,354.0	2,154.6
Other operating expenses									623.6	585.1	531.6
Supplies									167.9	158.7	149.3
Total operating expenses									3,912.5	3,647.7	3,264.5
Other income									(30.5)	(2.2)	(4.1)
Equity in net income of nonconsolidated affiliates									(6.7)	(8.7)	(8.0)
Noncontrolling interests	$ (22.6)	$ (21.9)	$ (19.7)	$ (22.9)	$ (19.6)	$ (20.7)	$ (21.4)	$ (21.4)	(87.1)	(83.1)	(79.1)
Inpatient Rehabilitation
Segment Reporting Information [Line Items]
Net operating revenues									3,513.0	3,346.2	3,141.3
Operating expenses:
Salaries and benefits									1,813.1	1,701.5	1,603.8
Other operating expenses									521.9	502.3	462.5
Supplies									147.0	140.6	135.7
Occupancy costs									64.8	63.8	61.9
Cost of services sold (excluding depreciation and amortization)									0.0	0.0	0.0
Support and overhead costs									0.0	0.0	0.0
Total operating expenses									2,546.8	2,408.2	2,263.9
Other income									(10.5)	(3.6)	(4.1)
Equity in net income of nonconsolidated affiliates									(5.5)	(7.5)	(7.3)
Noncontrolling interests									82.6	77.2	67.6
Segment Adjusted EBITDA									899.6	871.9	821.2
Capital expenditures									391.4	264.6	238.0
Home Health and Hospice Segment
Segment Reporting Information [Line Items]
Net operating revenues									1,092.0	931.1	772.6
Operating expenses:
Salaries and benefits									0.0	0.0	0.0
Other operating expenses									0.0	0.0	0.0
Supplies									0.0	0.0	0.0
Occupancy costs									0.0	0.0	0.0
Cost of services sold (excluding depreciation and amortization)									506.2	438.4	363.3
Support and overhead costs									381.7	323.5	277.2
Total operating expenses									887.9	761.9	640.5
Other income									0.0	(0.5)	0.0
Equity in net income of nonconsolidated affiliates									(1.2)	(1.2)	(0.7)
Noncontrolling interests									9.5	8.5	6.9
Segment Adjusted EBITDA									195.8	162.4	125.9
Capital expenditures									$ 12.7	$ 11.6	$ 10.7