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Significant Accounting Policies (Tables) | 12 Months Ended
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Dec. 31, 2011
Significant Accounting Policies |
Weighted average assumptions for the Black-Scholes method used to estimate fair value of stock option grants |
|  | 2011 |  | 2010 |  | 2009
--- | --- | --- | --- | --- | --- | ---
Range of expected lives of options (years) |  | 4.75 |  | 4.75 |  | 4.75
Range of expected stock price volatilities |  | 53.0% - 56.6% |  | 52.4% - 53.9% |  | 42.0% - 52.0%
Weighted average expected stock price volatilities |  | 53.2% |  | 53.3% |  | 46.3%
Range of risk-free interest rates |  | 0.8% - 2.1% |  | 1.2% - 2.5% |  | 1.3% - 2.1%
Expected dividend yield |  | 0.0% |  | 0.0% |  | 0.0%

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- Definition Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Topic 718 -SubTopic 10 -Publisher FASB -Number -Article -Subparagraph (f)(2) -Name Accounting Standards Codification -Paragraph 2 -Section 50 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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