Revenue and Related Matters - Schedule of Contract with Customer, Asset and Liability (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets:
Fees receivable, gross	$ 1,334,012	$ 1,262,818
Contract assets recorded in Prepaid expenses and other current assets	21,350	26,119
Contract liabilities:
Deferred revenues (current liability)	1,928,020	1,745,244
Non-current deferred revenues recorded in Other liabilities	24,409	21,194
Total contract liabilities	$ 1,952,429	$ 1,766,438