Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Expected Subscriber Fees (Details)

v3.8.0.1
Summary of Significant Accounting Policies - Expected Subscriber Fees (Details) - Subscriber Accounts
$ in Thousands
Dec. 31, 2017
USD ($)
Finite-Lived Intangible Assets [Line Items]  
2018 $ 201,427
2019 170,250
2020 149,189
2021 132,662
2022 $ 121,209