CONSOLIDATED FINANCIAL STATEMENT DETAILS - Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accrued expenses and other current liabilities:
Accrued employee compensation and benefits	$ 137,583	$ 108,431
Accrued advertising expense	105,520	96,445
Other	191,783	162,048
Accrued expenses and other current liabilities	$ 434,886	$ 366,924