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Stockholders' Equity - Summary of Preferred and Common Stock (Details) - $ / shares | Dec. 31, 2017 | Jun. 30, 2017 | Dec. 31, 2016
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Class Of Stock [Line Items] |  |  |
Common stock, voting par value | $ 0.01 | $ 0.01 |
Common stock, voting shares authorized | 150,000,000 |  | 150,000,000
Common stock, voting shares issued | 29,317,298 |  | 24,616,706
Common stock, voting shares outstanding | 29,317,298 |  | 24,616,706
Series A Non-cumulative Perpetual Preferred Stock |  |  |
Class Of Stock [Line Items] |  |  |
Par value |  |  | $ 0.01
Shares authorized |  |  | 15,003
Shares issued |  |  | 15,003
Shares outstanding |  |  | 15,003
Series B 7.5% Fixed Non-Cumulative Perpetual Preferred Stock |  |  |
Class Of Stock [Line Items] |  |  |
Par value | $ 0.01 |  | $ 0.01
Shares authorized | 50,000 |  | 50,000
Shares issued | 10,438 |  | 9,388
Subscription receivable |  |  | 1,050
Shares outstanding | 10,438 |  | 9,388

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