Employees, Retirement and Incentive Plans - Retirement and Benefit Plan Costs (Details) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
|
Sep. 30, 2022
USD ($)
plan
shares
|
Sep. 30, 2021
USD ($)
|
Sep. 30, 2022
USD ($)
component
plan
shares
|
Sep. 30, 2021
USD ($)
|
|
| Share-based Compensation Arrangements | ||||
| Retirement and benefit costs | $ | $ 2.8 | $ 2.1 | $ 7.9 | $ 6.2 |
| Number of long-term incentive plan components | component | 5 | |||
| Number of incentive-based award plans | plan | 2 | 2 | ||
| Compensation costs | $ | $ 0.3 | $ 0.6 | $ 1.5 | $ 1.9 |
| Long-term Incentive Plan | ||||
| Share-based Compensation Arrangements | ||||
| Units authorized to be granted (in shares) | shares | 2,500,000 | 2,500,000 | ||
| Units not yet granted (in shares) | shares | 848,570 | 848,570 | ||