Cash, Cash Equivalents, and Investments - Additional Information (Detail) (USD $)
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3 Months Ended | 6 Months Ended | ||||
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Jun. 30, 2013
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Jul. 01, 2012
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Jun. 30, 2013
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Jul. 01, 2012
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Jun. 30, 2013
Equity Securities [Member]
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Dec. 31, 2012
Equity Securities [Member]
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Schedule of Available-for-sale Securities [Line Items] | ||||||
Fair value | $ 1,669,000 | $ 2,131,000 | ||||
Gross unrealized loss | 462,000 | 462,000 | ||||
Gross realized gains on sale of investments | 101,000 | 1,233,000 | 150,000 | 1,327,000 | ||
Gross realized losses on sale of investments | 49,000 | 238,000 | 67,000 | 238,000 | ||
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 |