|
Benefit Plans (Details) (USD $)
In Millions, unless otherwise specified
|
3 Months Ended |
|
Mar. 31, 2015
|
Mar. 31, 2014
|
| Components of net periodic benefit cost |
|
|
| Contributions to qualified and non qualified pension plans |
$ 11.0 |
$ 1.9 |
| Qualified Pension Plan [Member] |
|
|
| Components of net periodic benefit cost |
|
|
| Contributions to qualified and non qualified pension plans |
10.0 |
|
| Pension Plan [Member] |
|
|
| Components of net periodic benefit cost |
|
|
| Service cost |
0.9 |
0.7 |
| Interest cost |
5.9 |
5.7 |
| Expected return on plan assets |
(6.7) |
(6.4) |
| Amortization of prior service benefit |
0 |
0 |
| Recognized net actuarial loss |
1.7 |
0.8 |
| Net periodic pension benefit cost |
1.8 |
0.8 |
| Other Benefits [Member] |
|
|
| Components of net periodic benefit cost |
|
|
| Service cost |
0 |
0 |
| Interest cost |
0.1 |
0.2 |
| Expected return on plan assets |
0 |
0 |
| Amortization of prior service benefit |
0 |
(0.1) |
| Recognized net actuarial loss |
0.1 |
0.1 |
| Net periodic pension benefit cost |
$ 0.2 |
$ 0.2 |