Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net income	$ 784,830	$ 814,888	$ 612,299
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property and equipment	47,940	46,352	46,330
Stock-based compensation	53,439	48,243	50,626
Other Noncash Income (Expense)	6,027	(9,108)	(11,926)
Changes in operating assets and liabilities
Prepaid expenses and other assets	(14,058)	(9,214)	(3,279)
Accounts payable and accrued liabilities	15,495	2,227	(24)
Deferred revenues	90,471	29,009	16,191
Net deferred income taxes and other long term tax liabilities	(176,992)	(192,214)	43,675
Net Cash Provided by (Used in) Operating Activities	807,152	730,183	753,892
Cash flows from investing activities:
Proceeds from maturities and sales of marketable securities	2,654,457	2,305,732	2,247,904
Purchases of marketable securities	(2,870,670)	(2,355,405)	(2,030,521)
Purchases of property and equipment	(53,033)	(43,395)	(40,316)
Payments for (Proceeds from) Businesses and Interest in Affiliates	0	20,810	(9,872)
Net cash provided by (used in) investing activities	(269,246)	(72,258)	167,195
Cash flows from financing activities:
Repayment of Borrowings	(750,000)	0	0
Proceeds from Debt, Net of Issuance Costs	741,053	0	0
Repurchases of common stock	(722,587)	(777,454)	(782,583)
Proceeds from issuance of common stock from option exercises and employee stock purchase plans	12,404	12,577	13,152
Proceeds from (Payments for) Other Financing Activities	0	0	(872)
Net cash used in financing activities	(719,130)	(764,877)	(770,303)
Effect of exchange rate changes on cash and cash equivalents	(561)	(48)	64
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	(181,785)	(107,000)	150,848
Cash and cash equivalents at end of period	223,487	401,194
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	228,816	410,601	517,601
Supplemental cash flow disclosures:
Cash paid for interest, net of capitalized interest	85,578	87,354	87,683
Cash paid for income taxes, net of refunds received	$ 178,351	$ 132,683	$ 89,974