Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Millions	Total	Common Stock	Capital in Excess of Par Value	Accumulated (Deficit) Income	Treasury Stock	Noncontrolling Interests
Balance at beginning of period (shares) at Dec. 31, 2018		98,900
Balance at beginning of period at Dec. 31, 2018	$ 1,557.0	$ 1.1	$ 2,588.7	$ (885.2)	$ (427.9)	$ 280.3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	433.2			358.7		74.5
Receipt of treasury stock (shares)		(300)
Receipt of treasury stock	(16.6)				(16.6)
Dividends declared	(109.3)		(109.3)
Stock-based compensation	32.4		32.4
Stock options exercised (shares)		100
Stock options exercised	1.4		1.4
Distributions declared	(70.2)					(70.2)
Repurchases of common stock in open market (in shares)		(800)
Repurchases of common stock in open market	(45.9)				(45.9)
Capital contributions from consolidated affiliates	20.0					20.0
Fair value adjustments to redeemable noncontrolling interests	(147.6)		(147.6)
Consolidation of Yuma Rehabilitation Hospital	25.0					25.0
Other (shares)		700
Other	13.7		4.3	0.0	(1.9)	11.3
Balance at end of period (shares) at Dec. 31, 2019		98,600
Balance at end of period at Dec. 31, 2019	1,693.1	$ 1.1	2,369.9	(526.5)	(492.3)	340.9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	361.4			284.2		77.2
Receipt of treasury stock (shares)		(200)
Receipt of treasury stock	(15.7)				(15.7)
Dividends declared	(111.6)		(111.6)
Stock-based compensation	29.5		29.5
Stock options exercised (shares)		100
Stock options exercised	1.1		1.1
Distributions declared	(72.1)					(72.1)
Repurchases of common stock in open market (in shares)		(100)
Repurchases of common stock in open market	(6.1)				(6.1)
Capital contributions from consolidated affiliates	42.8					42.8
Fair value adjustments to redeemable noncontrolling interests	1.4		1.4
Exchange of Holdings shares (shares)		600
Exchange of Holdings shares	46.3		27.1		19.2
Other (shares)		400
Other	(0.1)		9.2	0.0	(2.5)	(6.8)
Balance at end of period (shares) at Dec. 31, 2020		99,400
Balance at end of period at Dec. 31, 2020	1,970.0	$ 1.1	2,326.6	(242.3)	(497.4)	382.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	508.2			412.2		96.0
Receipt of treasury stock (shares)		(200)
Receipt of treasury stock	(16.4)				(16.4)
Dividends declared	(111.9)		(83.8)	(28.1)
Stock-based compensation	$ 32.8		32.8
Stock options exercised (shares)	8
Distributions declared	$ (87.8)					(87.8)
Capital contributions from consolidated affiliates	72.5					72.5
Other (shares)		300
Other	(10.4)		14.0	0.0	(7.4)	(17.0)
Balance at end of period (shares) at Dec. 31, 2021		99,500
Balance at end of period at Dec. 31, 2021	$ 2,357.0	$ 1.1	$ 2,289.6	$ 141.8	$ (521.2)	$ 445.7