Consolidated Statements Of Cash Flows - USD ($)	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flow from operating activities:
Net income	$ 143,544,000	$ 51,912,000
Adjustments to reconcile net income to net cash provided by operating activities:
Disposal gain on sale of business	(159,753,000)	0
Depreciation and amortization	38,341,000	35,984,000
Stock-based compensation	27,335,000	24,662,000
Deferred income taxes	2,711,000	2,268,000
Changes in operating assets and liabilities	49,320,000	(26,189,000)
Net cash provided by operating activities	101,498,000	88,637,000
Cash flow from investing activities:
Capital expenditures	(25,362,000)	(26,048,000)
Proceeds from sale of business, net of cash divested	160,266,000	0
Capitalization of internally developed software	(3,108,000)	(4,497,000)
Additions to other intangibles	(630,000)	(487,000)
Acquisitions of equity-method investments	0	(9,784,000)
Purchases of short-term investments	(206,330,000)	(91,777,000)
Sales and maturities of short-term investments	306,955,000	117,108,000
Net cash provided by (used in) investing activities	231,791,000	(15,485,000)
Cash flow from financing activities:
Proceeds from revolving line of credit	20,000,000	0
Proceeds from issuance of secured debt	70,000,000.0	0
Debt issuance costs	(1,480,000)	0
Proceeds from issuance of common stock	17,252,000	17,645,000
Repurchase of common stock	(23,680,000)	(92,375,000)
Dividends paid	(68,156,000)	(66,067,000)
Net cash provided by (used in) financing activities	13,936,000	(140,797,000)
Effect of exchange rate changes on cash	(636,000)	20,000
Net change in cash, cash equivalents and restricted cash	346,589,000	(67,625,000)
Cash, cash equivalents and restricted cash at beginning of period	194,616,000	259,386,000
Cash, cash equivalents and restricted cash at end of period	$ 541,205,000	$ 191,761,000