Business and Basis of Presentation - Schedule of Contract with Customer, Asset and Liability (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Assets:
Fees receivable, gross	$ 1,120,656	$ 1,262,818
Contract assets recorded in Prepaid expenses and other current assets	27,455	26,119
Contract liabilities:
Deferred revenues (current liability)	1,796,331	1,745,244
Non-current deferred revenues recorded in Other liabilities	16,396	21,194
Total contract liabilities	$ 1,812,727	$ 1,766,438