Revenue and Related Matters - Schedule of Contract with Customer, Asset and Liability (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Assets:
Fees receivable, gross	$ 1,157,565		$ 1,334,012
Contract assets recorded in Prepaid expenses and other current assets	19,558		21,350
Contract liabilities:
Deferred revenues (current liability)	1,847,384		1,928,020
Non-current deferred revenues recorded in Other liabilities	17,231		24,409
Total contract liabilities	1,864,615		$ 1,952,429
Revenue recognized previously attributable to deferred revenues	$ 658,400	$ 650,100