|
Derivative instruments and hedging activities (Details 3) (USD $)
In Millions, unless otherwise specified |
Jun. 30, 2013
|
Dec. 31, 2012
|
|---|---|---|
| Fair value of derivative instruments | ||
| Derivative Assets | $ 9.5 | $ 20.8 |
| Derivative Liabilities | 114.9 | 151.3 |
|
Derivative instruments designated as cash flow hedges
|
||
| Fair value of derivative instruments | ||
| Derivative Liabilities | 4.7 | 6.5 |
|
Derivative instruments designated as cash flow hedges | Interest rate swaps | Current
|
||
| Fair value of derivative instruments | ||
| Derivative Liabilities | 1.3 | 1.3 |
|
Derivative instruments designated as cash flow hedges | Interest rate swaps | Long-term
|
||
| Fair value of derivative instruments | ||
| Derivative Liabilities | 3.4 | 5.2 |
|
Derivative instruments not designated as cash flow hedges
|
||
| Fair value of derivative instruments | ||
| Derivative Assets | 9.5 | 20.8 |
| Derivative Liabilities | 110.2 | 144.8 |
|
Derivative instruments not designated as cash flow hedges | Interest rate swaps | Current
|
||
| Fair value of derivative instruments | ||
| Derivative Liabilities | 7.2 | 7.3 |
|
Derivative instruments not designated as cash flow hedges | Interest rate swaps | Long-term
|
||
| Fair value of derivative instruments | ||
| Derivative Assets | 7.3 | 0.1 |
| Derivative Liabilities | 12.9 | 27.7 |
|
Derivative instruments not designated as cash flow hedges | Foreign currency forward contracts | Current
|
||
| Fair value of derivative instruments | ||
| Derivative Assets | 0.9 | 9.5 |
| Derivative Liabilities | 0.3 | |
|
Derivative instruments not designated as cash flow hedges | Foreign currency forward contracts | Long-term
|
||
| Fair value of derivative instruments | ||
| Derivative Assets | 1.3 | 11.0 |
| Derivative Liabilities | 0.3 | |
|
Derivative instruments not designated as cash flow hedges | Natural gas swaps | Current
|
||
| Fair value of derivative instruments | ||
| Derivative Liabilities | 0.7 | |
|
Derivative instruments not designated as cash flow hedges | Natural gas swaps | Long-term
|
||
| Fair value of derivative instruments | ||
| Derivative Assets | 0.1 | |
| Derivative Liabilities | 3.8 | 3.9 |
|
Derivative instruments not designated as cash flow hedges | Gas purchase agreements | Current
|
||
| Fair value of derivative instruments | ||
| Derivative Assets | 0.1 | |
| Derivative Liabilities | 23.0 | 24.5 |
|
Derivative instruments not designated as cash flow hedges | Gas purchase agreements | Long-term
|
||
| Fair value of derivative instruments | ||
| Derivative Liabilities | $ 62.0 | $ 81.4 |