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Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands | 1 Months Ended | 6 Months Ended
--- | --- | ---
Feb. 28, 2019 | Apr. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2018
Class of Stock [Line Items] |  |  |  |
Proceeds from issuance of common stock, net of offering costs |  |  | $ 118,657 | $ 103,259
Firm Commitment Public Underwritten Offer |  |  |  |
Class of Stock [Line Items] |  |  |  |
Number of shares issued or sold (in shares) |  | 4,500,000 |  |
Common stock purchase price (in dollars per share) |  | $ 21.25 |  |
Proceeds from issuance of common stock, net of offering costs |  | $ 103,000 |  |
Over-allotment option |  |  |  |
Class of Stock [Line Items] |  |  |  |
Number of shares issued or sold (in shares) | 825,000 | 675,000 |  |
Common stock purchase price (in dollars per share) | $ 20.00 | $ 21.25 |  |
Follow-On Equity Offering |  |  |  |
Class of Stock [Line Items] |  |  |  |
Number of shares issued or sold (in shares) | 5,500,000 |  |  |
Common stock purchase price (in dollars per share) | $ 20.00 |  |  |
Proceeds from issuance of common stock, net of offering costs | $ 118,700 |  |  |

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