CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning Balance at Dec. 31, 2021	$ 1,430,093	$ 351	$ 914,802	$ 562,882	$ (47,942)
Beginning Balance, shares (in shares) at Dec. 31, 2021		175,481
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under stock option plans	9,861	$ 1	9,860
Issuance of common stock under stock option plans, shares		514
Repurchase of common stock	(204,314)	$ (7)		(204,307)
Repurchase of common stock, shares		(3,364)
Stock-based compensation expense	54,505		54,505
Payment of dividends ($0.305 per common share)	(45,921)			(45,921)
Net income	215,525			215,525
Net unrealized gain (loss), net of tax of $1,245, $4,389, and $(5,943) in 2024, 2023, and 2022, respectively	(17,152)				(17,152)
Net unrealized gain (loss) on available-for-sale investments, net of tax	(17,152)
Reclassification of net realized (gain) loss on the sale of available-for-sale investments	182				182
Foreign currency translation adjustments, net of tax	(4,385)				(4,385)
Balance at Dec. 31, 2022	1,438,394	$ 345	979,167	528,179	(69,297)
Balance, shares (in shares) at Dec. 31, 2022		172,631
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under stock option plans	3,268	$ 1	3,267
Issuance of common stock under stock option plans, shares		691
Repurchase of common stock	(79,794)	$ (3)		(79,791)
Repurchase of common stock, shares		(1,723)
Stock-based compensation expense	54,768		54,768
Payment of dividends ($0.305 per common share)	(49,079)			(49,079)
Net income	113,234			113,234
Net unrealized gain (loss), net of tax of $1,245, $4,389, and $(5,943) in 2024, 2023, and 2022, respectively	10,507				10,507
Net unrealized gain (loss) on available-for-sale investments, net of tax	10,507
Reclassification of net realized (gain) loss on the sale of available-for-sale investments	1,954				1,954
Foreign currency translation adjustments, net of tax	11,500				11,500
Balance at Dec. 31, 2023	$ 1,504,752	$ 343	1,037,202	512,543	(45,336)
Balance, shares (in shares) at Dec. 31, 2023	171,599	171,599
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under stock option plans	$ 994	$ 1	993
Issuance of common stock under stock option plans, shares	242	546
Repurchase of common stock	$ (67,085)	$ (3)		(67,082)
Repurchase of common stock, shares		(1,711)
Stock-based compensation expense	52,443		52,443
Payment of dividends ($0.305 per common share)	(52,329)			(52,329)
Net income	106,171			106,171
Net unrealized gain (loss), net of tax of $1,245, $4,389, and $(5,943) in 2024, 2023, and 2022, respectively	3,809				3,809
Net unrealized gain (loss) on available-for-sale investments, net of tax	3,809
Reclassification of net realized (gain) loss on the sale of available-for-sale investments	8				8
Foreign currency translation adjustments, net of tax	(31,258)				(31,258)
Balance at Dec. 31, 2024	$ 1,517,505	$ 341	$ 1,090,638	$ 499,303	$ (72,777)
Balance, shares (in shares) at Dec. 31, 2024	170,434	170,434