Revenue and Related Matters - Schedule of Contract with Customer, Asset and Liability (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Assets:
Fees receivable, gross	$ 975,966		$ 975,966		$ 1,251,508
Contract assets recorded in Prepaid expenses and other current assets	24,318		24,318		14,440
Contract liabilities:
Deferred revenues (current liability)	2,028,908		2,028,908		1,974,548
Non-current deferred revenues recorded in Other liabilities	52,043		52,043		26,754
Total contract liabilities	2,080,951		2,080,951		$ 2,001,302
Revenue recognized previously attributable to deferred revenues	$ 818,400	$ 681,600	$ 1,505,400	$ 1,354,200