Capital Stock (Details) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) vote / share $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 shares
Class Of Stock [Line Items]
Total Shares Authorized	210,000,000	210,000,000
Preferred Stock, Shares Authorized	10,000,000	10,000,000	10,000,000
Preferred Stock, Par Value | $ / shares	$ 0.01	$ 0.01	$ 0.01
Phantom Stock Value Per Share | $ / shares	$ 3.33	$ 3.33
Phantom Stock Units	860,244	860,244
SERP units	38,754	38,754	47,487
Treasury Stock, Shares, Acquired		800,000	9,300,000	14,200,000
Stock Repurchased During Period, Value | $	$ (649.6)	$ (75.8)	$ (800.0)
Class A [Member]
Class Of Stock [Line Items]
Common Stock, Shares Authorized	200,000,000	200,000,000	200,000,000
Common Stock, Par Value | $ / shares	$ 0.01	$ 0.01	$ 0.01
Vote Per Share | vote / share		1
Class B [Member]
Class Of Stock [Line Items]
Common Stock, Shares Authorized	0	0	0
Common Stock, Par Value | $ / shares	$ 0	$ 0	$ 0