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Stock-Based Compensation Plans (Details 5) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Additional disclosures    
Stock-based compensation expense $ 5,471 $ 3,846
Capitalized stock-based compensation cost $ 2,096 $ 2,086
Performance Shares    
Additional disclosures    
Grant date value (in dollars per share) $ 195.72  
Restricted stock and restricted stock units    
Additional disclosures    
Unrecognized compensation cost for unvested restricted stock $ 51,331  
Weighted average period for recognition of unrecognized compensation cost 2 years 7 months 6 days