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Capital Stock, Other Offerings and Agreements (Details) (USD $)
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12 Months Ended | 1 Months Ended | 11 Months Ended | 12 Months Ended | 11 Months Ended | 12 Months Ended | 1 Months Ended | ||||||||||
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Dec. 31, 2013
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Dec. 31, 2012
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Dec. 31, 2011
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Jun. 30, 2009
Registered Direct Offerings [Member]
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May 31, 2011
2010 ATM Agreement [Member]
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Dec. 31, 2011
2010 ATM Agreement [Member]
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Dec. 31, 2011
2011 ATM Agreement [Member]
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Dec. 31, 2013
2011 ATM Agreement [Member]
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Dec. 31, 2013
Underwritten Offering [Member]
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Aug. 31, 2013
Underwritten Offering [Member]
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Oct. 31, 2012
Underwritten Offering [Member]
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Mar. 31, 2012
Underwritten Offering [Member]
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Feb. 28, 2010
Underwritten Offering [Member]
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Dec. 18, 2013
Underwritten Offering [Member]
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Aug. 23, 2013
Underwritten Offering [Member]
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Oct. 29, 2012
Underwritten Offering [Member]
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Mar. 09, 2012
Underwritten Offering [Member]
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| Registered Direct Offerings and Underwritten Offering [Abstract] | |||||||||||||||||
| Capital units issued (in shares) | 695,652 | 2,800,000 | 10,925,000 | 8,736,187 | 13,333,333 | 29,669,154 | |||||||||||
| Common stock per capital unit (in shares) | 1 | 1 | 0.5 | ||||||||||||||
| Common stock per capital unit called by stock warrant (in shares) | 0.5 | 0.45 | |||||||||||||||
| Gross proceeds from issuance of capital units | $ 12,000,000 | $ 57,400,000 | $ 31,600,000 | $ 40,000,000 | $ 39,200,000 | $ 21,000,000 | |||||||||||
| Offering expense | 800,000 | 1,000,000 | 100,000 | 3,800,000 | 2,200,000 | 3,000,000 | 3,000,000 | ||||||||||
| Purchase price of capital units (in dollars per share) | $ 17.25 | $ 5.25 | $ 3.62 | $ 3.00 | $ 1.32 | ||||||||||||
| Number of shares called by warrants (in shares) | 347,826 | 14,834,577 | |||||||||||||||
| Exercise price of warrants (in dollars per share) | $ 19.50 | $ 1.76 | |||||||||||||||
| Period to purchase additional stock | 30 days | 30 days | 30 days | ||||||||||||||
| Term of warrants | 5 years | ||||||||||||||||
| Warrant outstanding (in shares) | 12,562,682 | ||||||||||||||||
| ATM Agreement [Abstract] | |||||||||||||||||
| Common stock sold (in shares) | 7,560,862 | 821,386 | 7,572,327 | 0 | |||||||||||||
| Sales commission paid per transaction (in hundredths) | 3.00% | ||||||||||||||||
| Proceeds from issuance of common stock | $ 84,338,000 | $ 76,498,000 | $ 15,143,000 | $ 34,000,000 | $ 4,400,000 | $ 14,600,000 | $ 500,000 | ||||||||||