Pensions and Postretirement Benefits (Summary of Change in Defined Benefit and Postretirement Benefit Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Change in plan assets
Fair value of plan assets at beginning of year	$ 117.3
Fair value of plan assets at end of year	120.2	$ 117.3
Funded (underfunded) status of the plans
Pension assets	61.7	58.9
Pension Benefits
Change in benefit obligation
Benefit obligation at beginning of year	58.4	61.1
Service costs	2.4	2.6	$ 2.2
Interest costs	1.8	2.3	2.2
Actuarial losses (gains)	0.5	(3.0)
Benefits and expenses paid, net of contributions	(4.6)	(4.6)
Benefit obligation at end of year	58.5	58.4	61.1
Change in plan assets
Fair value of plan assets at beginning of year	117.3	125.7
Actual return on plan assets	8.3	(2.9)
Company contributions	0.0	0.0
Cash transfer to fund postretirement benefit payments	(0.8)	(0.9)
Benefits and expenses paid, net of contributions	(4.6)	(4.6)
Fair value of plan assets at end of year	120.2	117.3	125.7
Funded (underfunded) status of the plans	61.7	58.9
Funded (underfunded) status of the plans
Pension assets	61.7	58.9
Other current liabilities	0.0	0.0
Other long-term liabilities	0.0	0.0
Total assets (liabilities) recognized in the consolidated balance sheets	61.7	58.9
Amounts recognized in Accumulated other comprehensive loss
Net actuarial loss	25.8	25.2
Net prior service cost (credit)	0.3	0.3
Accumulated other comprehensive loss	26.1	25.5
Postretirement Benefits
Change in benefit obligation
Benefit obligation at beginning of year	13.5	17.0
Service costs	0.0	0.0	0.0
Interest costs	0.3	0.5	0.6
Actuarial losses (gains)	(2.6)	(2.7)
Benefits and expenses paid, net of contributions	(1.2)	(1.3)
Benefit obligation at end of year	10.0	13.5	17.0
Change in plan assets
Fair value of plan assets at beginning of year	0.0	0.0
Actual return on plan assets	0.0	0.0
Company contributions	1.2	1.3
Cash transfer to fund postretirement benefit payments	0.0	0.0
Benefits and expenses paid, net of contributions	(1.2)	(1.3)
Fair value of plan assets at end of year	0.0	0.0	$ 0.0
Funded (underfunded) status of the plans	(10.0)	(13.5)
Funded (underfunded) status of the plans
Pension assets	0.0	0.0
Other current liabilities	1.2	1.4
Other long-term liabilities	8.8	12.1
Total assets (liabilities) recognized in the consolidated balance sheets	(10.0)	(13.5)
Amounts recognized in Accumulated other comprehensive loss
Net actuarial loss	1.7	4.4
Net prior service cost (credit)	(0.2)	(0.3)
Accumulated other comprehensive loss	$ 1.5	$ 4.1