Revenue and Related Matters - Schedule of Contract with Customer, Asset and Liability (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Assets:
Fees receivable, gross	$ 1,184,426		$ 1,251,508
Contract assets recorded in Prepaid expenses and other current assets	19,883		14,440
Contract liabilities:
Deferred revenues (current liability)	2,088,463		1,974,548
Non-current deferred revenues recorded in Other liabilities	25,852		26,754
Total contract liabilities	2,114,315		$ 2,001,302
Revenue recognized previously attributable to deferred revenues	$ 726,700	$ 658,400