Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity (Details)

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Stockholders' Equity (Details) - USD ($)
 1 Months Ended 3 Months Ended 9 Months Ended
May 29, 2018
May 31, 2014
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Oct. 31, 2018
Jun. 05, 2018
Jun. 04, 2018
Dec. 31, 2017
Class of Stock [Line Items]                    
Proceeds from public offering, net of underwriters’ discount and offering costs         $ 441,794,000 $ 0        
Offering expenses $ 17,100,000                  
Common stock, shares authorized (in shares)     250,000,000   250,000,000     250,000,000 125,000,000 125,000,000
Authorized amount of common stock repurchase   $ 50,000,000                
Number of shares repurchased (in shares)     0 0 0 0        
Common Stock                    
Class of Stock [Line Items]                    
Repurchase period (in years)   1 year                
Public Stock Offering                    
Class of Stock [Line Items]                    
Number of shares issued in underwritten common stock offering (in shares) 8,050,000                  
Proceeds from public offering, net of underwriters’ discount and offering costs $ 458,900,000                  
Proceeds from public offering, net of underwriters’ discount and offering costs $ 441,800,000                  
Over-Allotment Option                    
Class of Stock [Line Items]                    
Number of shares issued in underwritten common stock offering (in shares) 1,050,000                  
Sale of stock price (in dollars per share) $ 57                  
Subsequent Event                    
Class of Stock [Line Items]                    
Authorized amount of common stock repurchase             $ 100,000,000.0