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Statements of Stockholders' Equity (Unaudited) (Parenthetical) - shares
3 Months Ended 6 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2019
Statement of Stockholders' Equity [Abstract]        
Exercise of stock options, net of cashless exercise of shares 8,958 21,864 11,409 21,864