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Summary of Significant Accounting Policies Net Income Per Share (Details) (USD $)
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3 Months Ended | 12 Months Ended | 9 Months Ended | |||||||||
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Dec. 31, 2011
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Sep. 30, 2011
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Jun. 30, 2011
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Mar. 31, 2011
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Dec. 31, 2010
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Sep. 30, 2010
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Jun. 30, 2010
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Mar. 31, 2010
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Dec. 31, 2011
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Dec. 31, 2010
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Dec. 31, 2009
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Sep. 30, 2011
Convertible Debt Securities [Member]
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| Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] | ||||||||||||
| NET INCOME | $ 22,767,000 | $ 26,206,000 | $ 17,156,000 | $ 23,339,000 | $ 34,311,000 | $ 35,515,000 | $ 34,963,000 | $ 48,827,000 | $ 89,468,000 | $ 153,616,000 | $ 87,256,000 | |
| WEIGHTED AVERAGE NUMBER OF COMMON SHARES OUTSTANDING — BASIC | 45,411,000 | 44,084,000 | 43,295,000 | |||||||||
| Weighted Average Number Diluted Shares Outstanding Adjustment | 603,000 | 740,000 | 1,032,000 | |||||||||
| WEIGHTED AVERAGE NUMBER OF COMMON SHARES OUTSTANDING — DILUTED | 46,014,000 | 44,824,000 | 44,327,000 | |||||||||
| NET INCOME PER COMMON SHARE — BASIC | $ 0.50 | $ 0.58 | $ 0.38 | $ 0.52 | $ 0.77 | $ 0.81 | $ 0.80 | $ 1.12 | $ 1.97 | $ 3.48 | $ 2.02 | |
| Dilutive Securities, Effect on Basic Earnings Per Share | $ (0.03) | $ (0.05) | $ (0.05) | |||||||||
| NET INCOME PER COMMON SHARE — DILUTED | $ 0.49 | $ 0.57 | $ 0.37 | $ 0.51 | $ 0.76 | $ 0.79 | $ 0.78 | $ 1.10 | $ 1.94 | $ 3.43 | $ 1.97 | |
| Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount | 0.0 | 100,000 | 3,900,000 | |||||||||
| Class of Warrant or Right, Outstanding | 4,000,000 | |||||||||||
| X | ||||||||||
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- Definition
Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Aggregate amount of each class of warrants or rights outstanding. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Includes adjustments resulting from the assumption that dilutive convertible securities were converted, options or warrants were exercised, or that other shares were issued upon the satisfaction of certain conditions. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Details
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| X | ||||||||||
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- Definition
The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The portion of profit or loss for the period, net of income taxes, which is attributable to the parent. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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