CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) shares in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning Balance at Dec. 31, 2019	$ 1,355,710,000	$ 345,000	$ 639,372,000	$ 753,268,000	$ (37,275,000)
Beginning Balance, shares (in shares) at Dec. 31, 2019		172,440
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under stock option plans	125,715,000	$ 9,000	125,706,000
Issuance of common stock under stock option plans, shares		4,565
Repurchase of common stock	(51,036,000)	$ (2,000)		(51,034,000)
Repurchase of common stock, shares		(1,215)
Stock-based compensation expense	42,661,000		42,661,000
Payment of dividends ($0.265 per common share)	(390,508,000)			(390,508,000)
Net income	176,186,000			176,186,000
Net unrealized gain (loss), net of tax of $(5,943), $(2,206), and $981 in 2022, 2021, and 2020, respectively	6,478,000				6,478,000
Net unrealized gain (loss) on available-for-sale investments, net of tax	6,478,000
Reclassification of net realized (gain) loss on the sale of available-for-sale investments	(4,119,000)				(4,119,000)
Foreign currency translation adjustments, net of tax	1,115,000				1,115,000
Balance at Dec. 31, 2020	1,262,202,000	$ 352,000	807,739,000	487,912,000	(33,801,000)
Balance, shares (in shares) at Dec. 31, 2020		175,790
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under stock option plans	63,292,000	$ 3,000	63,289,000
Issuance of common stock under stock option plans, shares		1,703
Repurchase of common stock	(161,652,000)	$ (4,000)		(161,648,000)
Repurchase of common stock, shares		(2,012)
Stock-based compensation expense	43,774,000		43,774,000
Payment of dividends ($0.265 per common share)	(43,263,000)			(43,263,000)
Net income	279,881,000			279,881,000
Net unrealized gain (loss), net of tax of $(5,943), $(2,206), and $981 in 2022, 2021, and 2020, respectively	(7,152,000)				(7,152,000)
Net unrealized gain (loss) on available-for-sale investments, net of tax	(7,152,000)
Reclassification of net realized (gain) loss on the sale of available-for-sale investments	(236,000)				(236,000)
Foreign currency translation adjustments, net of tax	(6,753,000)				(6,753,000)
Balance at Dec. 31, 2021	$ 1,430,093,000	$ 351,000	914,802,000	562,882,000	(47,942,000)
Balance, shares (in shares) at Dec. 31, 2021	175,481	175,481
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under stock option plans	$ 9,861,000	$ 1,000	9,860,000
Issuance of common stock under stock option plans, shares	365	514
Repurchase of common stock	$ (204,314,000)	$ (7,000)		(204,307,000)
Repurchase of common stock, shares		(3,364)
Stock-based compensation expense	54,505,000		54,505,000
Payment of dividends ($0.265 per common share)	(45,921,000)			(45,921,000)
Net income	215,525,000			215,525,000
Net unrealized gain (loss), net of tax of $(5,943), $(2,206), and $981 in 2022, 2021, and 2020, respectively	(17,152,000)				(17,152,000)
Net unrealized gain (loss) on available-for-sale investments, net of tax	(17,152,000)
Reclassification of net realized (gain) loss on the sale of available-for-sale investments	182,000				182,000
Foreign currency translation adjustments, net of tax	(4,385,000)				(4,385,000)
Balance at Dec. 31, 2022	$ 1,438,394,000	$ 345,000	$ 979,167,000	$ 528,179,000	$ (69,297,000)
Balance, shares (in shares) at Dec. 31, 2022	172,631	172,631