Consolidated Statement of Shareholders' Equity - USD ($) shares in Thousands, $ in Millions	Total	Common Stock	Capital in Excess of Par Value	Accumulated Deficit	Accumulated Other Comprehensive Loss	Treasury Stock	Noncontrolling Interests
Balance at beginning of period (shares) at Dec. 31, 2016		88,900
Balance at beginning of period at Dec. 31, 2016	$ 910.6	$ 1.1	$ 2,781.0	$ (1,448.4)	$ (1.2)	$ (614.7)	$ 192.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	332.3			271.1			61.2
Receipt of treasury stock (shares)		(900)
Receipt of treasury stock	(19.8)					(19.8)
Dividends declared ($1.10 in 2019, $1.04 in 2018 and $0.98 in 2017)	(95.2)		(95.2)
Stock-based compensation	21.3		21.3
Stock options exercised (shares)		1,100
Stock options exercised	1.1		20.4			(19.3)
Stock warrants exercised (shares)		700
Stock warrants exercised	26.6		26.6
Distributions declared	(50.5)						(50.5)
Repurchases of common stock in open market (shares)		(900)
Repurchases of common stock in open market	(38.1)					(38.1)
Capital contributions from consolidated affiliates	46.2						46.2
Fair value adjustments to redeemable noncontrolling interests	(67.0)		(67.0)
Conversion of convertible debt, net of tax (shares)		8,900
Conversion of convertible debt, net of tax	328.2		53.7			274.5
Other (shares)		500
Other	(0.3)		6.6	1.1	(0.1)	(1.1)	(6.8)
Balance at end of period (shares) at Dec. 31, 2017		98,300
Balance at end of period at Dec. 31, 2017	1,395.4	$ 1.1	2,747.4	(1,176.2)	(1.3)	(418.5)	242.9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	361.5			292.3			69.2
Receipt of treasury stock (shares)		(200)
Receipt of treasury stock	(8.3)					(8.3)
Dividends declared ($1.10 in 2019, $1.04 in 2018 and $0.98 in 2017)	(103.7)		(103.7)
Stock-based compensation	28.9		28.9
Stock options exercised (shares)		100
Stock options exercised	3.2		3.2			0.0
Distributions declared	(71.1)						(71.1)
Capital contributions from consolidated affiliates	38.8						38.8
Fair value adjustments to redeemable noncontrolling interests	(91.0)		(91.0)
Other (shares)		700
Other	3.3		3.9	(1.3)	1.3	(1.1)	0.5
Balance at end of period (shares) at Dec. 31, 2018		98,900
Balance at end of period at Dec. 31, 2018	1,557.0	$ 1.1	2,588.7	(885.2)	0.0	(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 ($1.10 in 2019, $1.04 in 2018 and $0.98 in 2017)	(109.3)		(109.3)
Stock-based compensation	$ 32.4		32.4
Stock options exercised (shares)	78	100
Stock options exercised	$ 1.4		1.4			0.0
Distributions declared	(70.2)						(70.2)
Repurchases of common stock in open market (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			(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)	$ 0.0	$ (492.3)	$ 340.9