Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity At-the-Market Offering (Details)

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Stockholders' Equity At-the-Market Offering (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Subsidiary, Sale of Stock [Line Items]      
Number of shares authorized to be sold under equity distribution agreement (in shares) 35,000,000 10,000,000  
Number of common shares issued under equity distribution agreement and outstanding as of period-end (in shares) 7,490,235    
Accumulated proceeds from issuance of common shares under equity distribution agreement $ 128,600    
Number of shares of stock issued during period (in shares)     26,950
At the Market Offering [Member]      
Subsidiary, Sale of Stock [Line Items]      
Number of shares of stock issued during period (in shares) 3,697,300 0 0
Issuance of stock, net of offering costs $ 51,000 $ 0 $ 0