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Cash, Cash Equivalents and Investments - Additional Information (Detail) - USD ($) | 12 Months Ended
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Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items] |  |  |
Cash balance included foreign bank balance | $ 39,279,000 | $ 43,732,000 |
Gross realized gains on sale of debt securities | 549,000 | 843,000 | $ 508,000
Gross realized losses on sale of debt securities | 205,000 | 170,000 | $ 194,000
Maximum amount committed to invest in limited partnership | 20,500,000 |  |
Contribution to limited partnership | 19,886,000 |  |
Remaining amount of commitment in limited partnership | 614,000 |  |
Proceeds from Limited Partnership Investments | 1,014,000 |  |
Carrying value of investment | 942,000 | $ 1,956,000 |
Cost Method Investments, Fair Value Disclosure | $ 5,600,000 |  |

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