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Non-Marketable Investments - Additional Information (Detail) (USD $) | 3 Months Ended | 9 Months Ended |  |  |  | 3 Months Ended | 9 Months Ended |
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Sep. 30, 2013 | Sep. 30, 2013 | Dec. 31, 2012 | Sep. 30, 2013 Technology Related Private Equity Funds [Member] | Dec. 31, 2012 Technology Related Private Equity Funds [Member] | Sep. 30, 2012 Non-marketable Investments [Member] | Sep. 30, 2013 Non-marketable Investments [Member] | Sep. 30, 2012 Non-marketable Investments [Member] | Sep. 30, 2013 Maximum [Member] Participant | Sep. 30, 2013 Minimum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |  |  |  |  |  |  |  |  |
Carrying value of the Company's non-marketable investments |  |  |  | $ 6,200,000 | $ 6,600,000 |  |  |  |  |
Ownership interest of company |  |  |  |  |  |  |  |  |  | 5.00%
Gain (losses) from non-marketable investments | 0 |  |  |  |  | 800,000 | (100,000) | 900,000 |  |
Book value of investment | 900,000 | 900,000 | 1,200,000 |  |  |  |  |  |  |
Bonus paid under cash bonus plan |  | $ 0 |  |  |  |  |  |  |  |
Cash bonus plan expiration date |  | Jun. 30, 2015 |  |  |  |  |  |  |  |
Participant in the cash bonus plan |  |  |  |  |  |  |  |  | 10 |

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