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Stock-Based Compensation - Summary of Stock Option Activity (Details) (USD $)
In Thousands, except Share data, unless otherwise specified
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12 Months Ended |
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Dec. 31, 2013
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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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| Number of Stock Options Outstanding |
|
|
|
|
| Shares, beginning balance |
7,426,417 |
8,229,597 |
7,268,909 |
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| Shares, granted |
1,720,242 |
1,339,129 |
1,570,684 |
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| Shares, exercised |
(2,031,903) |
(1,747,213) |
(368,194) |
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| Shares, cancelled |
(646,013) |
(395,096) |
(241,802) |
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| Shares, ending balance |
6,468,743 |
7,426,417 |
8,229,597 |
7,268,909 |
| Shares, exercisable as of December 31, 2013 |
3,957,414 |
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|
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| Shares, vested and expected to vest as of December 31, 2013 |
6,028,954 |
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| Weighted-Average Exercise Price |
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| Weighted average exercise price, beginning balance |
$ 3.57 |
$ 2.52 |
$ 1.48 |
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| Weighted average exercise price, granted |
$ 7.53 |
$ 8.12 |
$ 7.13 |
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| Weighted average exercise price, exercised |
$ 1.31 |
$ 1.39 |
$ 1.26 |
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| Weighted average exercise price, cancelled |
$ 7.40 |
$ 6.63 |
$ 3.28 |
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| Weighted average exercise price, ending balance |
$ 4.96 |
$ 3.57 |
$ 2.52 |
$ 1.48 |
| Weighted average exercise price, exercisable as of December 31, 2013 |
$ 3.40 |
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|
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| Weighted average exercise price, vested and expected to vest as of December 31, 2013 |
$ 4.77 |
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| Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term |
6 years 7 months 2 days |
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|
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| Weighted average remaining contractual life (years), balance |
6 years 8 months 12 days |
6 years 5 months |
6 years 7 months |
6 years 11 months |
| Weighted average remaining contractual life (years), exercisable as of December 31, 2013 |
5 years 4 months 24 days |
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| Aggregate Intrinsic Value |
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| Aggregate intrinsic value, beginning balance |
$ 40,040 |
$ 50,541 |
$ 13,937 |
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| Aggregate intrinsic value, exercised |
11,816 |
9,558 |
2,854 |
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| Aggregate intrinsic value, ending balance |
8,991 |
40,040 |
50,541 |
13,937 |
| Aggregate intrinsic value, exercisable as of December 31, 2013 |
8,839 |
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| Aggregate intrinsic value, vested and expected to vest as of December 31, 2013 |
$ 8,983 |
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