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Stock-Based Compensation (Details 2) (USD $)
|
12 Months Ended |
|---|---|
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Dec. 31, 2012
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| Summary of restricted stock units | |
| Non-vested at December 31, 2011 | 589,117 |
| Non-Vested Shares Awarded | 497,291 |
| Non-Vested Shares Vested | (293,813) |
| Non-Vested Shares Cancelled/forfeited | (48,579) |
| Non-vested at December 31, 2012 | 744,016 |
| Weighted Average Grant Date Fair Value, Non-vested at December 31,2011 | $ 19.22 |
| Weighted Average Grant Date Fair Value, Awarded | $ 24.55 |
| Weighted Average Grant Date Fair Value, Vested | $ 16.90 |
| Weighted Average Grant Date Fair Value, Cancelled/forfeited | $ 22.18 |
| Weighted Average Grant Date Fair Value, Non-vested at December 31,2012 | $ 23.51 |