Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity (Details)

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Stockholders' Equity (Details) - USD ($)
3 Months Ended 12 Months Ended
May. 06, 2014
Mar. 31, 2016
Dec. 31, 2015
May. 31, 2015
Class of Stock [Line Items]        
Authorized amount of common stock repurchase $ 50,000,000     $ 50,000,000.0
Repurchase period (in years) 1 year      
Stock repurchased during period   $ 16,100,000 $ 35,100,000  
Number of shares repurchased during the period (in shares)   777,669 1,798,199  
Weighted average cost per share of shares repurchased (in dollars per share)   $ 20.75 $ 19.51  
Common Stock        
Class of Stock [Line Items]        
Stock repurchased during period   $ 1,000    
Number of shares repurchased during the period (in shares)   777,669 2,764,794