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Investment in AquaBounty - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified | 9 Months Ended | 12 Months Ended | 0 Months Ended | 1 Months Ended | 9 Months Ended | 12 Months Ended | 9 Months Ended
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Sep. 30, 2013 | Sep. 30, 2012 | Dec. 31, 2012 | Dec. 31, 2011 | Mar. 15, 2013 AquaBounty [Member] | Nov. 29, 2012 AquaBounty [Member] | Nov. 16, 2012 AquaBounty [Member] | Feb. 28, 2013 AquaBounty [Member] | Jan. 31, 2013 AquaBounty [Member] | Sep. 30, 2013 AquaBounty [Member] | Sep. 30, 2012 AquaBounty [Member] | Dec. 31, 2012 AquaBounty [Member] | Sep. 30, 2013 AquaBounty [Member] In- Process Research and Development [Member]
Business Combination Transactions [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Number of shares acquired |  |  |  |  |  |  | 48,631,444 |  |  |  |  |  |
Percentage of outstanding shares |  |  |  |  |  |  | 47.56% |  |  |  |  |  |
Definitive purchase agreement amount |  |  |  |  |  |  | $ 6,000 |  |  |  |  |  |
Carrying amount of the investment | 5,000 |  | 5,726 |  |  |  |  |  |  |  |  | 5,726 |
Fair value of the investment |  |  |  |  |  |  |  |  |  |  |  | 14,300 |
Amount of loan allowed in promissory note |  |  |  |  |  | 500 |  |  |  |  |  |  |
Annual interest rate |  |  |  |  |  | 3.00% |  |  |  |  |  |  |
Amount drawn on promissory note | 300 |  | 200 |  |  |  |  | 100 | 200 |  |  | 200 |
Promissory note repaid | 500 | 34 | 34 | 300 | 500 |  |  |  |  |  |  |  |
Maturity date of promissory note |  |  |  |  |  | May 28, 2013 |  |  |  |  |  |  |
Number of shares acquired |  |  |  |  | 18,714,814 |  |  |  |  |  |  |  |
Amount from private subscription offering |  |  |  |  | 4,907 |  |  |  |  |  |  |  |
Aggregate percentage of ownership |  |  |  |  | 53.82% |  |  |  |  |  |  |  |
Gain recognized | $ 7,415 |  |  |  | $ 7,415 |  |  |  |  | $ 7,400 | $ 7,400 |  |
Percentage of equity interest previously held |  |  |  |  | 47.56% |  |  |  |  |  |  |  |
Expected useful life of intangible asset |  |  |  |  |  |  |  |  |  |  |  |  | 15 years

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