CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Revenues	$ 996,810	$ 875,059	$ 789,582
Cost of revenues (exclusive of depreciation, shown separately below)	525,122	449,820	394,811
Other operating expenses:
Research and development	127,994	124,034	113,215
Selling, general and administrative	191,329	169,308	153,695
Depreciation	21,422	18,304	13,380
Restructuring and reorganization charges	4,834	8,661	8,796
Total operating expenses	870,701	770,127	683,897
Operating income	126,109	104,932	105,685
Other income (expense):
Interest expense	(17,748)	(17,667)	(16,794)
Amortization of original issue discount	(2,819)	(2,664)	(2,790)
Interest and investment income, net	1,785	2,646	3,246
Loss on extinguishment of debt		(810)
Other, net	(1,604)	550	(1,637)
Total other	(20,386)	(17,945)	(17,975)
Income before income taxes	105,723	86,987	87,710
Income tax provision	(22,953)	(20,857)	(26,346)
Net income	$ 82,770	$ 66,130	$ 61,364
Weighted-average shares outstanding:
Basic	32,051	32,488	32,415
Diluted	32,465	32,855	32,865
Earnings per common share:
Basic	$ 2.58	$ 2.04	$ 1.89
Diluted	$ 2.55	$ 2.01	$ 1.87