Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating activities:
Net income	$ 164,100	$ 75,097
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	56,264	54,696
Stock-based compensation expense	36,086	25,129
Deferred taxes	3,883	25,537
Reduction in the carrying amount of operating lease right-of-use assets	18,575	22,862
Amortization and write-off of deferred financing fees	923	1,637
Gain on de-designated swaps	(15,765)	0
Changes in assets and liabilities:
Fees receivable, net	54,192	135,661
Deferred commissions	(237)	17,520
Prepaid expenses and other current assets	(9,933)	(12,656)
Other assets	(10,081)	5,961
Deferred revenues	131,786	(26,228)
Accounts payable and accrued and other liabilities	(272,495)	(269,467)
Cash provided by operating activities	157,298	55,749
Investing activities:
Additions to property, equipment and leasehold improvements	(12,521)	(24,536)
Cash used in investing activities	(12,521)	(24,536)
Financing activities:
Proceeds from employee stock purchase plan	5,357	5,641
Proceeds from revolving credit facility	0	27,000
Payments on revolving credit facility	(5,000)	0
Payments on borrowings	(5,127)	(27,967)
Purchases of treasury stock	(398,450)	(73,164)
Cash used in financing activities	(403,220)	(68,490)
Net decrease in cash and cash equivalents	(258,443)	(37,277)
Effects of exchange rates on cash and cash equivalents	(8,145)	(15,709)
Cash and cash equivalents, beginning of period	712,583	280,836
Cash and cash equivalents, end of period	$ 445,995	$ 227,850