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Shareholders' Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands | 9 Months Ended |
--- | --- | ---
Sep. 30, 2017 | Sep. 30, 2016 | Jan. 10, 2017
Class of Stock [Line Items] |  |  |
Net proceeds from issuance of common stock | $ 219,504 | $ 94,538 |
Underwritten Public Equity Offering [Member] | Common Stock [Member] |  |  |
Class of Stock [Line Items] |  |  |
Shares issued |  |  | 26,450,000
Price per share issued (in dollars per share) |  |  | $ 8.65
Net proceeds from issuance of common stock | $ 220,000 |  |

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