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Subsequent Events - Additional Information (Detail) - Common Stock [Member] - USD ($) $ / shares in Units, $ in Millions | 1 Months Ended
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Apr. 30, 2019 | Apr. 30, 2018
Subsequent Event [Line Items] |  |
Total shares issued |  | 14,200,000
Public offering price of common stock issued |  | $ 16.25
Net proceeds from issuance of common stock, after deducting offering expenses |  | $ 215.8
Subsequent Event [Member] |  |
Subsequent Event [Line Items] |  |
Total shares issued | 12,650,000 |
Public offering price of common stock issued | $ 11.50 |
Net proceeds from issuance of common stock, after deducting offering expenses | $ 136.2 |
Subsequent Event [Member] | Underwriters [Member] |  |
Subsequent Event [Line Items] |  |
Total shares issued | 1,650,000 |

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