| Components of Net Periodic Benefit (Income) Cost |
| | | | | | | | | | | | | | | | | | Pension Benefits | | Other Postretirement
Benefits | | Three Months Ended
September 30, | | Three Months Ended
September 30, | | 2016 | | 2015 | | 2016 | | 2015 | Components of Net Periodic Benefit (Income) Cost | ($ in millions) | Service cost | $ | 3.3 |
| | $ | 1.5 |
| | $ | 0.2 |
| | $ | 0.3 |
| Interest cost | 21.8 |
| | 20.5 |
| | 0.3 |
| | 0.4 |
| Expected return on plans’ assets | (39.5 | ) | | (35.4 | ) | | — |
| | — |
| Amortization of prior service cost | (0.1 | ) | | — |
| | (2.0 | ) | | — |
| Recognized actuarial loss | 5.2 |
| | 7.4 |
| | 0.2 |
| | 0.6 |
| Net periodic benefit (income) cost | $ | (9.3 | ) | | $ | (6.0 | ) | | $ | (1.3 | ) | | $ | 1.3 |
|
| | | | | | | | | | | | | | | | | | Pension Benefits |
| Other Postretirement
Benefits | | Nine Months Ended
September 30, |
| Nine Months Ended
September 30, | | 2016 |
| 2015 |
| 2016 |
| 2015 | Components of Net Periodic Benefit (Income) Cost | ($ in millions) | Service cost | $ | 9.2 |
|
| $ | 4.4 |
|
| $ | 0.9 |
|
| $ | 0.9 |
| Interest cost | 66.0 |
|
| 61.7 |
|
| 1.2 |
|
| 1.7 |
| Expected return on plans’ assets | (118.4 | ) |
| (106.7 | ) |
| — |
|
| — |
| Amortization of prior service cost | — |
| | 0.1 |
| | (2.0 | ) | | — |
| Recognized actuarial loss | 15.5 |
|
| 22.3 |
|
| 1.8 |
|
| 2.4 |
| Curtailments/settlements | — |
|
| 0.1 |
|
| — |
|
| 0.1 |
| Net periodic benefit (income) cost | $ | (27.7 | ) |
| $ | (18.1 | ) |
| $ | 1.9 |
|
| $ | 5.1 |
|
|