XML 52 R38.htm IDEA: XBRL DOCUMENT v3.8.0.1
Stockholders' Equity - Equity Offerings (Detail) - USD ($)
$ / shares in Units, $ in Millions
 1 Months Ended 3 Months Ended 5 Months Ended 12 Months Ended
May 31, 2017
Jun. 30, 2016
Dec. 31, 2017
May 23, 2017
Dec. 31, 2017
Dec. 31, 2016
Common Stock            
Equity offerings            
Issuance of common stock, net of issuance costs, shares 8,050,000 3,476,793     11,038,647 4,145,584
Weighted average price per share issued $ 11.50 $ 6.10        
Aggregate net proceeds from stock sale $ 86.8 $ 19.7        
At The Market Equity Offering            
Equity offerings            
Common stock available for sale under agreement     $ 80.0   $ 80.0  
At The Market Equity Offering | Common Stock            
Equity offerings            
Issuance of common stock, net of issuance costs, shares     1,600,000 1,388,647   668,791
Weighted average price per share issued     $ 12.50 $ 5.55 $ 12.50 $ 6.336
Aggregate net proceeds from stock sale     $ 19.3 $ 7.4   $ 3.9