Business and Basis of Presentation - Schedule of Contract with Customer, Asset and Liability (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Assets:
Fees receivable, gross	$ 1,186,559		$ 1,262,818
Contract assets	29,852		26,119
Contract liabilities:
Deferred revenues (current liability)	1,837,504		1,745,244
Non-current deferred revenues	17,333		21,194
Total contract liabilities	1,854,837		$ 1,766,438
Revenue recognized previously attributable to deferred revenues	$ 650,100	$ 605,500