Pension and Other Postretirement Benefit Plans (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2017 |
Jun. 30, 2016 |
Jun. 30, 2017 |
Jun. 30, 2016 |
|
| Pension Plans [Member] | ||||
| Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | ||||
| Service cost - benefits earned during the period | $ 0.2 | $ 0.4 | ||
| Interest cost | $ 6.5 | 7.4 | $ 12.9 | 14.8 |
| Expected return on plan assets | (6.8) | (7.5) | (13.6) | (15.0) |
| Recognized net actuarial loss | 3.8 | 2.8 | 7.6 | 5.6 |
| Net periodic pension cost (benefit) | 3.5 | 2.9 | 6.9 | 5.8 |
| Postretirement Plans [Member] | ||||
| Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | ||||
| Interest cost | 0.1 | 0.1 | 0.2 | 0.2 |
| Recognized net actuarial loss | 0.1 | 0.1 | 0.1 | |
| Amortization of prior service cost | (0.4) | (0.3) | (0.7) | (0.7) |
| Net periodic pension cost (benefit) | $ (0.2) | $ (0.2) | $ (0.4) | $ (0.4) |