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Stock-Based Compensation Plans (Details 5) - USD ($)
$ / shares in Units, $ in Thousands
6 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Additional disclosures    
Stock-based compensation expense $ 13,129 $ 9,843
Capitalized stock-based compensation cost $ 5,374 $ 5,490
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 $ 41,250  
Weighted average period for recognition of unrecognized compensation cost 2 years 3 months 18 days