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Accounts Payable and Accrued Liabilities (Narrative) (Details) (USD $) In Millions, unless otherwise specified | Dec. 31, 2012 | Dec. 31, 2011
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Accounts Payable and Accrued Liabilities, Current [Abstract] |  |
Accrued liabilities for lease turnover costs, total | $ 42.5 |
Accrued liabilities for lease turnover costs, noncurrent | 10.3 | 42.6
Accrued liabilities for lease turnover costs, current | $ 32.2 |

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