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Fair Value Measurements, Derivatives (Details) (Derivative [Member], USD $)
In Millions, unless otherwise specified |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
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Sep. 30, 2013
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Sep. 30, 2012
|
Sep. 30, 2013
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Sep. 30, 2012
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Derivative [Member]
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| Fair value of derivatives classified as Level 3 in the fair value hierarchy | ||||
| Beginning Balance | $ 9.2 | $ 9.9 | $ 4.7 | $ 5.7 |
| Realized and unrealized gains (losses) | 0 | 0 | 0 | 0 |
| Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases | 0 | 0 | 10.6 | 10.9 |
| Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales | 0 | 0 | 0 | 0 |
| Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements | (3.6) | (2.6) | (9.7) | (9.3) |
| Transfers in and/or out of Level 3 | 0 | 0 | 0 | 0 |
| Ending Balance | 5.6 | 7.3 | 5.6 | 7.3 |
| Change in unrealized gains (losses) relating to instruments still held as of period end | $ 0 | $ 0 | $ 0 | $ 0 |