Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net income	$ 653,138	$ 602,753
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense	115,174	115,706
Depreciation expense	28,834	26,821
(Decrease) increase in fair value of contingent consideration	(3,900)	1,600
Deferred income taxes	57,043	36,705
Losses on equity securities	52,295	44,870
Other non-cash items, net	2,332	9,668
Changes in operating assets and liabilities:
Accounts receivable, net	(98,373)	(223,672)
Inventories	(22,785)	(27,450)
Prepaid expenses and other assets	(13,319)	2,790
Accounts payable	(10,644)	14,285
Accrued expenses	152,983	153,814
Other liabilities	8,277	57,808
Net cash provided by operating activities	921,055	815,698
Cash flows from investing activities:
Purchases of available-for-sale debt securities	(121,455)	(75,265)
Maturities of available-for-sale debt securities	118,072	60,145
Sale of equity securities	0	72,036
Purchases of property and equipment	(70,926)	(19,450)
Investment in equity securities	0	(5,800)
Net cash (used in) provided by investing activities	(74,309)	31,666
Cash flows from financing activities:
Issuances of common stock under benefit plans	15,559	79,597
Repurchases of common stock	(424,952)	(300,026)
Payments in connection with common stock withheld for employee tax obligations	(102,140)	(136,167)
Payments on finance leases	(12,233)	(10,287)
Proceeds from finance leases	3,632	5,833
Other financing activities	1,480	1,620
Net cash used in financing activities	(518,654)	(359,430)
Effect of changes in exchange rates on cash	(4,030)	(6,651)
Net increase in cash, cash equivalents and restricted cash	324,062	481,283
Cash, cash equivalents and restricted cash—beginning of period	5,988,845	3,120,681
Cash, cash equivalents and restricted cash—end of period	6,312,907	3,601,964
Supplemental disclosure of cash flow information:
Cash paid for interest	14,534	13,771
Cash paid for income taxes	$ 10,691	$ 5,845