|
Retirement Benefits - Narrative (Details) (USD $)
In Millions, except Share data, unless otherwise specified |
3 Months Ended | 6 Months Ended | ||||
|---|---|---|---|---|---|---|
|
Jun. 30, 2012
|
Mar. 31, 2012
|
Jun. 30, 2011
|
Jun. 30, 2012
|
Jun. 30, 2011
|
Sep. 30, 2012
|
|
| Net periodic pension cost (credit) [Line Items] | ||||||
| UMWA obligation increase due to "Cadillac" plan excise tax | $ 1.3 | $ 3.7 | $ 7.3 | $ 3.7 | ||
| Retirement Benefit Plan Remeasurements [Abstract] | ||||||
| Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year | 15.5 | 15.5 | ||||
| Cash portion of contribution | 7.0 | |||||
| Newly issued shares of common stock for contribution | 361,446 | |||||
| Common stock value per share for stock contribution | $ 24.90 | |||||
| Aggregate value of shares of common stock contribution | 9.0 | 9.0 | ||||
| 2010 Healthcare reform black lung obligation increase | $ 12.2 | $ 0 | $ 12.2 | $ 0 | ||