Summary of Significant Accounting Policies - Reconciliation of the Basic and Diluted EPS Denominators (Details) - shares shares in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of the basic and diluted EPS denominators
Basic weighted-average common shares	32,415	30,968	31,051
Dilutive effect of restricted common stock	444	603	624
Dilutive effect of 2010 Convertible Notes		1,062	1,633
Dilutive effect of Stock Warrants	6	381	130
Diluted weighted-average common shares	32,865	33,014	33,438

Weighted average number of shares issued diluted.

No definition available.

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- Definition

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of call options and warrants using the treasury stock method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 23
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=96947427&loc=d3e1757-109256

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-Publisher FASB
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- Definition

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of convertible debt securities using the if-converted method.

+ References

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-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

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- Definition

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

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- Definition

This element represents the weighted average total number of shares issued throughout the period including the first (beginning balance outstanding) and last (ending balance outstanding) day of the period before considering any reductions (for instance, shares held in treasury) to arrive at the weighted average number of shares outstanding. Weighted average relates to the portion of time within a reporting period that common shares have been issued and outstanding to the total time in that period. Such concept is used in determining the weighted average number of shares outstanding for purposes of calculating earnings per share (basic).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
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-Section 45
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-URI http://asc.fasb.org/extlink&oid=96947427&loc=d3e1448-109256

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- References

No definition available.

+ Details

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