Pensions and Postretirement Benefits Other Than Pensions (Schedule of Company's Postretirement Plans Benefit Obligations) (Details) - Postretirement [Member] - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Benefit obligation at beginning of year		$ 442.7	$ 528.0
Service cost		2.6	2.8
Interest cost		14.8	14.4
Plan participants' contributions		7.7	9.1
Actuarial (gains) losses		6.7	(60.4)
Benefits paid, net of Medicare Part D subsidy	[1]	(45.6)	(50.2)
Other, including expenses paid		(0.1)	(1.0)
Benefit obligation at end of year		$ 428.8	$ 442.7

[1] Amounts are net of Medicare Part D subsidy of $0.8 million and $0.9 million in 2019 and 2018, respectively