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Financial Instruments - Fair Value of Interest Rate Derivatives by Balance Sheet Location (Details) (USD $)
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Sep. 30, 2013
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Dec. 31, 2012
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|---|---|---|
| Derivatives, Fair Value [Line Items] | ||
| Collateral deposited | $ 921,701 | $ 890,609 |
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Interest Rate Contract [Member] | Designated as Hedging Instrument [Member] | Other Current Liabilities [Member]
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| Derivatives, Fair Value [Line Items] | ||
| Interest Rate Derivative Liabilities, at Fair Value | 0 | 21,290,000 |
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Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member] | Non-current Liabilities [Member]
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| Derivatives, Fair Value [Line Items] | ||
| Interest Rate Derivative Liabilities, at Fair Value | 0 | 5,134,000 |
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Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member] | Other Current Liabilities [Member]
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| Derivatives, Fair Value [Line Items] | ||
| Interest Rate Derivative Liabilities, at Fair Value | 8,270,000 | 0 |
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Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member] | Noncurrent Derivative Assets [Member]
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| Derivatives, Fair Value [Line Items] | ||
| Interest Rate Derivative Assets, at Fair Value | $ 64,309,000 | $ 0 |