Revenue and Related Matters - Schedule of Contract with Customer, Asset and Liability (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Assets:
Fees receivable, gross	$ 1,110,562		$ 1,110,562		$ 1,251,508
Contract assets recorded in Prepaid expenses and other current assets	22,637		22,637		14,440
Contract liabilities:
Deferred revenues (current liability)	2,152,043		2,152,043		1,974,548
Non-current deferred revenues recorded in Other liabilities	31,826		31,826		26,754
Total contract liabilities	2,183,869		2,183,869		$ 2,001,302
Revenue recognized previously attributable to deferred revenues	$ 817,300	$ 692,600	$ 1,261,900	$ 1,087,900