Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity (Details)

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Stockholders' Equity (Details)
$ / shares in Units, $ in Millions
 1 Months Ended 6 Months Ended 12 Months Ended
Jul. 26, 2018
Jul. 12, 2018
$ / shares
shares
May 10, 2018
$ / shares
Feb. 28, 2017
USD ($)
$ / shares
shares
Jun. 30, 2018
$ / shares
shares
Dec. 31, 2017
$ / shares
Class of Stock [Line Items]            
Common stock, par value (in dollars per share) | $ / shares         $ 0.166667 $ 0.166667
Preferred stock, par value (in dollars per share) | $ / shares         1 $ 1
Preferred stock, liquidation preference per share (in dollars per share) | $ / shares         $ 100  
Issuance of common stock and mandatory convertible preferred stock | $       $ 72.3    
Preferred dividend percentage         7.25% 7.25%
Convertible preferred stock, terms of conversion, measurement period         20 days  
Preferred stock, dividends per share, declared (in dollars per share) | $ / shares     $ 1.8125      
Subsequent Event            
Class of Stock [Line Items]            
Rights declared during period (in shares)   1        
Exercise price of rights (in dollars per share) | $ / shares   $ 52.50        
Period following public announcement of acquisition of 10% or more of outstanding shares   10 days        
Period following tender offer for acquisition   10 days        
Discount rate in the event that rights become exercisable   50.00%        
Reverse stock split, conversion ratio 15          
Common Stock            
Class of Stock [Line Items]            
Common stock, shares issued       800,000    
Stock issued, price per share (in dollars per share) | $ / shares       $ 2.10    
Common Stock | Subsequent Event            
Class of Stock [Line Items]            
Number of shares convertible in the event of rights becoming exercisable   2        
Common Stock | Minimum            
Class of Stock [Line Items]            
Convertible preferred stock, shares issued upon conversion         2.7605  
Common Stock | Maximum            
Class of Stock [Line Items]            
Convertible preferred stock, shares issued upon conversion         3.1746  
Preferred Stock            
Class of Stock [Line Items]            
Common stock, shares issued       500,000    
Series A Preferred Stock            
Class of Stock [Line Items]            
Preferred dividend percentage         7.25%  
Series A Preferred Stock | Subsequent Event            
Class of Stock [Line Items]            
Shares called by rights   0.001