Summary of Significant Accounting Policies - Customer Liabilities (Details) - USD ($)
$ in Thousands
Dec. 31, 2015
Dec. 31, 2014
Accounting Policies [Abstract]    
Deferred customer billings, current $ 130,124 $ 132,063
Accrued service costs, current 70,656 68,077
Customer deposits, current 1,641 19,675
Deferred revenue, current 95 183
Current portion of customer liabilities 202,516 219,998
Deferred customer billings, non-current 431,944 317,065
Customer deposits, non-current 533 0
Non current portion of customer liabilities 432,477 317,065
Total customer liabilities $ 634,993 $ 537,063