Revenue and Related Matters - Schedule of Contract with Customer, Asset and Liability (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Assets:
Fees receivable, gross	$ 1,059,519		$ 1,059,519		$ 1,334,012
Contract assets recorded in Prepaid expenses and other current assets	22,696		22,696		21,350
Contract liabilities:
Deferred revenues (current liability)	1,765,264		1,765,264		1,928,020
Non-current deferred revenues recorded in Other liabilities	17,664		17,664		24,409
Total contract liabilities	1,782,928		1,782,928		$ 1,952,429
Revenue recognized previously attributable to deferred revenues	$ 692,600	$ 708,300	$ 1,087,900	$ 1,062,000