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Stock Plans (Details) (USD $)
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12 Months Ended |
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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Stock options
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| Stock Plans |
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| Term of stock option grants |
10 years |
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| Vesting period |
4 years |
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| Summary of stock option activity |
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| Outstanding at beginning of the period (in shares) |
2,484,844 |
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| Granted (in shares) |
235,000 |
226,341 |
358,000 |
| Exercised (in shares) |
(38,005) |
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| Forfeited (in shares) |
(386,871) |
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| Expired (in shares) |
(114,732) |
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| Outstanding at the end of the period (in shares) |
2,180,236 |
2,484,844 |
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| Exercisable at end of the period (vested) (in shares) |
1,482,505 |
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| Weighted-Average Exercise Price |
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| Outstanding at the beginning of the period (in dollars per share) |
$ 17.79 |
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| Granted (in dollars per share) |
$ 10.06 |
$ 20.45 |
$ 26.09 |
| Exercised / vested (in dollars per share) |
$ 7.09 |
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| Forfeited (in dollars per share) |
$ 16.77 |
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| Expired (in dollars per share) |
$ 19.84 |
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| Outstanding at the end of the period (in dollars per share) |
$ 17.13 |
$ 17.79 |
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| Exercisable at end of the period (vested) (in dollars per share) |
$ 16.92 |
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2011 Plan
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| Stock Plans |
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| Maximum number of shares of common stock with respect to which awards may be granted |
2,779,466 |
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| Number of shares of common stock available for future grant |
1,093,024 |
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