Borrowing Arrangements - Maturities of Debt and Interest Expense (Details 4) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Borrowing Arrangements
Principal payments on debt outstanding in 2016	$ 7.5
Principal payments on debt outstanding in 2017	11.2
Principal payments on debt outstanding in 2018	7.5
Principal payments on debt outstanding in 2019	7.5
Principal payments on debt outstanding in 2020	77.7
Interest Expense
Interest expense	0.8	$ 0.3	$ 0.5
Interest costs capitalized	$ 0.4	$ 0.6	$ 0.4

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Amount of interest capitalized, including amount of allowance for funds used during construction.

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-Publisher FASB
-Name Accounting Standards Codification
-Glossary Allowance for Funds Used during Construction
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Amount of the cost of borrowed funds accounted for as interest expense for debt.

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-Publisher FASB
-Name Accounting Standards Codification
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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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