Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities:
Net income	$ 233,290	$ 122,456	$ 3,279
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	211,779	255,601	240,171
Stock-based compensation expense	69,008	66,172	78,943
Deferred taxes	(55,787)	1,524	(217,414)
Loss (gain) from divested operations	2,075	(45,447)	0
Gain on sale of an equity security	(9,120)	0	0
Reduction in the carrying amount of operating lease right-of-use assets	86,466
Amortization and write-off of deferred financing fees	6,497	13,815	15,062
Changes in assets and liabilities, net of acquisitions and divestitures:
Fees receivable, net	(66,729)	(115,003)	(368,516)
Deferred commissions	(30,315)	(31,247)	(61,393)
Prepaid expenses and other current assets	18,985	(50,551)	13,251
Other assets	(27,303)	11,456	(18,529)
Deferred revenues	181,203	187,147	382,852
Accounts payable and accrued and other liabilities	(54,613)	55,235	186,811
Cash provided by operating activities	565,436	471,158	254,517
Investing activities:
Additions to property, equipment and leasehold improvements	(149,016)	(126,873)	(110,765)
Acquisitions - cash paid (net of cash acquired)	(25,989)	(15,855)	(2,641,780)
Divestitures - cash received (net of cash transferred)	0	526,779	0
Proceeds from the sale of an equity security	14,120	0	0
Cash (used in) provided by investing activities	(160,885)	384,051	(2,752,545)
Financing activities:
Proceeds from employee stock purchase plan	17,629	14,689	11,711
Proceeds from borrowings	5,000	0	3,025,000
Payments for deferred financing fees	0	0	(51,171)
Payments on borrowings	(109,579)	(1,010,972)	(404,438)
Purchases of treasury stock	(199,042)	(260,832)	(41,272)
Cash (used in) provided by financing activities	(285,992)	(1,257,115)	2,539,830
Net increase (decrease) in cash and cash equivalents and restricted cash	118,559	(401,906)	41,802
Effects of exchange rates on cash and cash equivalents and restricted cash	3,614	(6,489)	25,902
Cash and cash equivalents and restricted cash, beginning of year	158,663	567,058	499,354
Cash and cash equivalents and restricted cash, end of year	280,836	158,663	567,058
Cash paid during the year for:
Interest	102,298	117,500	98,500
Income taxes, net of refunds received	$ 119,156	$ 95,800	$ 76,100