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Cash, Cash Equivalents, and Investments - Additional Information (Detail) (USD $) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 29, 2013 | Jun. 30, 2013 | Sep. 30, 2012 | Sep. 29, 2013 | Sep. 30, 2012 | Sep. 29, 2013 Equity Securities [Member] | Dec. 31, 2012 Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |  |  |
Gross realized gains on sale of investments | $ 32,000 |  | $ 342,000 | $ 182,000 | $ 1,669,000 |  |
Gross realized losses on sale of investments | 12,000 |  | 1,000 | 79,000 | 239,000 |  |
Fair value |  |  |  |  |  | 1,864,000 | 2,131,000
Net unrealized loss |  |  |  | 267,000 |  | 267,000 |
Maximum amount committed to invest in limited partnership |  |  |  | 20,500,000 |  |  |
Contribution to limited partnership | 19,886,000 |  |  | 19,886,000 |  |  |
Remaining amount of commitment in limited partnership | 614,000 |  |  | 614,000 |  |  |
Investment expiration date |  |  |  | Dec. 31, 2013 |  |  |
Number of contributions made during the period |  |  |  | 0 |  |  |
Cash distribution received |  | $ 1,285,000 |  |  |  |  |

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