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Commitments and Contingencies - Operating Leases - Additional Information (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Leases [Abstract]      
Rent expense, including other facility expenses $ 11,064 $ 8,593 $ 8,610
Rental income under sublease agreement 137 $ 1,051 $ 1,486
Expected future rental income under sublease agreement, 2018 104    
Expected future rental income under sublease agreement, 2019 120    
Expected future rental income under sublease agreement, 2020 55    
Expected future rental income under sublease agreement, 2021 56    
Expected future rental income under sublease agreement, 2022 58    
Expected future rental income under sublease agreement, thereafter $ 310