Supplemental Balance Sheet Information (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Other assets:
Long-term investments	$ 311,417	$ 435,612
Deferred marketing costs	0	35,668
Contract assets and cost to obtain a contract	42,287	0
Other	59,535	69,471
Total	413,239	540,751
Accounts payable and accrued liabilities:
Accounts payable	285,592	284,857
Customer deposits	700,397	693,005
Employee related liabilities	230,044	251,545
Other	185,602	229,447
Total	$ 1,401,635	$ 1,458,854