Retirement Plans - Expected Benefit Payments (Details) $ in Millions |
Dec. 31, 2016
USD ($)
|
|---|---|
| Pension Plan | |
| Defined Benefit Plan Disclosure [Line Items] | |
| 2017 | $ 16.8 |
| 2018 | 16.9 |
| 2019 | 16.7 |
| 2020 | 17.5 |
| 2021 | 18.1 |
| 2022-2026 | 91.5 |
| Other Postretirement Benefit Plan | |
| Defined Benefit Plan Disclosure [Line Items] | |
| 2017 | 0.1 |
| 2018 | 0.1 |
| 2019 | 0.1 |
| 2020 | 0.1 |
| 2021 | 0.1 |
| 2022-2026 | $ 0.4 |