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Organization and Nature of Operations - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified | 12 Months Ended | 0 Months Ended
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Dec. 31, 2013 | Oct. 16, 2013 IPO [Member]
Organization And Nature Of Business [Line Items] |  |
MacroGenics incorporated date | Aug. 14, 2000 |
Initial public offering number of share sold |  | 5,750,000
Initial public offering price per share |  | $ 16.00
Proceeds from initial public offering before offering expenses |  | $ 85.6

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