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Summary of Significant Accounting Policies (Foreign Currency Exchange) (Details) $ in Millions | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($) | Dec. 31, 2013
--- | --- | --- | ---
Significant Transactions |  |  |
Net unrealized foreign currency translation losses | $ (145.6) | $ (79.8) |
SEK |  |  |
Significant Transactions |  |  |
Foreign currency exchange rate | 8.4247 | 7.7737 | 6.4339
GBP |  |  |
Significant Transactions |  |  |
Foreign currency exchange rate | 0.6757 | 0.6426 | 0.6044
Euro Member Countries, Euro |  |  |
Significant Transactions |  |  |
Foreign currency exchange rate | 0.9189 | 0.8245 | 0.7259

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