Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity (Narratives) (Details)

v3.7.0.1
Stockholders' Equity (Narratives) (Details) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Common Stock    
Shares repurchased value $ 5,573 $ 11,551
Other Nonoperating Income (Expense) [Member]    
Share-based Compensation    
Share-based compensation expense 3,100 $ 2,300
Restricted Stock [Member]    
Share-based Compensation    
Unrecognized share-based compensation expense $ 21,000  
Weighted average period for recognition of unvested shares 1 year 10 months 28 days  
Restricted Stock [Member] | Stock Option Plan Member [Member]    
Share-based Compensation    
Granted (USD per share) $ 20.83 $ 18.16
Fair value of awards vesting during period $ 5,700 $ 1,500
Maximum [Member] | Restricted Stock [Member]    
Share-based Compensation    
Vesting period 3 years  
Common Stock - Class A [Member]    
Common Stock    
Shares repurchased value   $ 1,557
Share-based Compensation    
Number of shares authorized 15,700,000.0  
Common Stock - Class A [Member] | Stock Option Plan Member [Member]    
Share-based Compensation    
Number of shares available for grant 1,100,000  
Stock Buyback Program [Member]    
Common Stock    
Shares repurchased 200,000 600,000
Stock Buyback Program [Member] | Common Stock - Class A [Member]    
Common Stock    
Shares repurchased value $ 4,000 $ 11,100