Retirement and Postretirement Plans (Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Components of net periodic benefit cost (income)
Service cost	$ 0.2	$ 0.9	$ 0.6
Interest cost	1.5	4.6	4.7
Expected return on plan assets	(1.0)	(8.7)	(8.5)
Amortization of net actuarial losses	1.3	1.3	0.3
Net periodic pension (cost) income before special termination benefits	2.0	(1.9)	(2.9)
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements	(3.0)	0.0	0.0
Special termination benefits expense	0.0	0.0	0.3
Total net periodic benefit income	$ (1.0)	$ (1.9)	$ (2.6)
Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount Yield (as a percent)	3.78%	3.22%
Discount rate (as a percent)	3.88%
Pension Costs [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate (as a percent)		3.91%
Long-Duration Contracts, Assumptions by Product and Guarantee, Estimated Average Investment Yield	3.00%	6.00%