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Stockholders' Equity (Public Offering of Common Stock) (Details) - USD ($) |  |  | 3 Months Ended | 9 Months Ended
--- | --- | --- | --- | ---
Sep. 05, 2018 | Aug. 07, 2018 | Sep. 30, 2019 | Sep. 30, 2019 | Sep. 30, 2018
Subsidiary, Sale of Stock [Line Items] |  |  |  |  |
Issuance costs |  |  |  | $ 0 | $ 350,000
Public Offering |  |  |  |  |
Subsidiary, Sale of Stock [Line Items] |  |  |  |  |
Shares Issued |  | 50,875,000 |  |  |
Gross Proceeds Per Share (USD per share) |  | $ 7.78 |  |  |
Gross Proceeds |  | $ 395,807,000 |  |  |
Shares issues (in shares) | 875,000 |  |  |  |
Issuance costs | $ 6,400,000 |  |  |  |
At The Market |  |  |  |  |
Subsidiary, Sale of Stock [Line Items] |  |  |  |  |
Shares Issued |  |  | 982,350 |  |
Gross Proceeds |  |  | $ 7,100,000 |  |
Issuance costs |  |  | $ 72,000 |  |

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