Employee Benefits Schedule of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Pension Plan and SERP [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost		$ 0.2	$ 0.3
Interest cost		1.1	1.2
Expected return on plan assets		(1.4)	(1.3)
Amortization of prior service costs	[1]	0.2	0.3
Amortization of actuarial losses	[1]	0.3	0.3
Periodic expense		0.4	0.8
Medical Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amortization of prior service costs	[1]	(0.1)	(0.1)
Periodic expense		$ (0.1)	$ (0.1)

[1] Amortization of prior service costs and actuarial losses out of accumulated other comprehensive income are recognized on the Condensed Consolidated Statements of Operations within "Interest and other income (expense)".