CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive (Loss) Income	Treasury stock	Total
Balance at Dec. 31, 2019	$ 3,182	$ 4,397,511	$ 5,022,480	$ (32,387)	$ (5,219,505)	$ 4,171,281
Balance (in shares) at Dec. 31, 2019	636,460				(99,762)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation		17,098				17,098
Exercise of stock options	$ 4	13,971				13,975
Exercise of stock options (in shares)	644
Unrealized gain, net on available-for-sale securities				304		304
Repurchase of common stock					$ (579,948)	(579,948)
Repurchase of common stock (in shares)					(10,503)
Foreign currency translation				(30,599)		(30,599)
Net income			278,835			278,835
Balance at Mar. 31, 2020	$ 3,186	4,428,580	5,301,315	(62,682)	$ (5,799,453)	3,870,946
Balance (in shares) at Mar. 31, 2020	637,104				(110,265)
Balance at Dec. 31, 2019	$ 3,182	4,397,511	5,022,480	(32,387)	$ (5,219,505)	4,171,281
Balance (in shares) at Dec. 31, 2019	636,460				(99,762)
Increase (Decrease) in Stockholders' Equity
Net income						937,858
Balance at Sep. 30, 2020	$ 3,192	4,513,743	5,960,338	(32,529)	$ (5,815,423)	4,629,321
Balance (in shares) at Sep. 30, 2020	638,458				(110,565)
Balance at Mar. 31, 2020	$ 3,186	4,428,580	5,301,315	(62,682)	$ (5,799,453)	3,870,946
Balance (in shares) at Mar. 31, 2020	637,104				(110,265)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation		15,936				15,936
Exercise of stock options	$ 4	29,863				29,867
Exercise of stock options (in shares)	820
Unrealized gain, net on available-for-sale securities				200		200
Repurchase of common stock					$ (15,822)	(15,822)
Repurchase of common stock (in shares)					(298)
Foreign currency translation				9,044		9,044
Net income			311,369			311,369
Balance at Jun. 30, 2020	$ 3,190	4,474,379	5,612,684	(53,438)	$ (5,815,275)	4,221,540
Balance (in shares) at Jun. 30, 2020	637,924				(110,563)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation		17,668				17,668
Exercise of stock options	$ 2	21,696				21,698
Exercise of stock options (in shares)	534
Unrealized gain, net on available-for-sale securities				308		308
Repurchase of common stock					$ (148)	(148)
Repurchase of common stock (in shares)					(2)
Foreign currency translation				21,217		21,217
Net income			347,654			347,654
Balance at Sep. 30, 2020	$ 3,192	4,513,743	5,960,338	(32,529)	$ (5,815,423)	4,629,321
Balance (in shares) at Sep. 30, 2020	638,458				(110,565)
Balance at Dec. 31, 2020	$ 3,193	4,537,982	6,432,074	3,034	$ (5,815,423)	5,160,860
Balance (in shares) at Dec. 31, 2020	638,662				(110,565)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation	$ 0	17,949	0	0	$ 0	17,949
Exercise of stock options	$ 3	6,758	0	0	0	6,761
Exercise of stock options (in shares)	492
Unrealized gain, net on available-for-sale securities	$ 0	0	0	24	0	24
Repurchase of common stock	0	0	0	0	$ (13,419)	(13,419)
Repurchase of common stock (in shares)					(150)
Foreign currency translation	0	0	0	(27,932)	$ 0	(27,932)
Net income	0	0	315,194	0	0	315,194
Balance at Mar. 31, 2021	$ 3,196	4,562,689	6,747,268	(24,874)	$ (5,828,842)	5,459,437
Balance (in shares) at Mar. 31, 2021	639,154				(110,715)
Balance at Dec. 31, 2020	$ 3,193	4,537,982	6,432,074	3,034	$ (5,815,423)	$ 5,160,860
Balance (in shares) at Dec. 31, 2020	638,662				(110,565)
Increase (Decrease) in Stockholders' Equity
Exercise of stock options (in shares)						845
Net income						$ 1,056,161
Balance at Sep. 30, 2021	$ 3,199	4,626,299	7,488,235	(43,495)	$ (5,829,241)	6,244,997
Balance (in shares) at Sep. 30, 2021	639,851				(110,719)
Balance at Mar. 31, 2021	$ 3,196	4,562,689	6,747,268	(24,874)	$ (5,828,842)	5,459,437
Balance (in shares) at Mar. 31, 2021	639,154				(110,715)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation	$ 0	16,921	0	0	$ 0	16,921
Exercise of stock options	$ 2	17,723	0	0	$ 0	17,725
Exercise of stock options (in shares)	422				0
Unrealized loss, net on available-for-sale securities	$ 0	0	0	(183)	$ 0	(183)
Repurchase of common stock	$ 0	0	0	0	$ (399)	(399)
Repurchase of common stock (in shares)	0				(4)
Foreign currency translation	$ 0	0	0	8,235	$ 0	8,235
Net income	0	0	403,762	0	0	403,762
Balance at Jun. 30, 2021	$ 3,198	4,597,333	7,151,030	(16,822)	$ (5,829,241)	5,905,498
Balance (in shares) at Jun. 30, 2021	639,576				(110,719)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation	$ 0	16,293	0	0	$ 0	16,293
Exercise of stock options	$ 1	12,673	0	0	0	12,674
Exercise of stock options (in shares)	275
Unrealized loss, net on available-for-sale securities	$ 0	0	0	(43)	0	(43)
Foreign currency translation	0	0	0	(26,716)	0	(26,716)
Net income	0	0	337,205	0	0	337,205
Balance at Sep. 30, 2021	$ 3,199	$ 4,626,299	$ 7,488,235	$ (43,495)	$ (5,829,241)	$ 6,244,997
Balance (in shares) at Sep. 30, 2021	639,851				(110,719)