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Summary of Significant Accounting Policies - Revenue - Summary of Deferred Revenue Liabilities (Details) - USD ($)
$ in Thousands
Mar. 31, 2018
Jan. 01, 2018
Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]      
Deferred revenue $ 267,925   $ 241,590
Other Long-term Liabilities 96,731   $ 73,039
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09      
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]      
Deferred revenue 10,482 $ 9,953  
Other Long-term Liabilities $ 9,639 $ 9,453