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Summary of Significant Accounting Policies - Share Based Compensation (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share-based compensation                      
Stock compensation expense $ 9,791 $ 12,897 $ 13,795 $ 13,901 $ 14,601 $ 11,961 $ 9,550 $ 4,472 $ 50,384 $ 40,584 $ 21,252
Vesting period                 3 years    
Minimum                      
Share-based compensation                      
Estimated forfeitures (as a percent)                 0.00% 0.00% 0.00%
Maximum                      
Share-based compensation                      
Estimated forfeitures (as a percent)                 4.00% 4.00% 4.00%