CONDENSED CONSOLIDATED STATEMENTS OF INCOME - UNAUDITED - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Revenues	$ 245,856	$ 213,033	$ 490,649	$ 414,737
Cost of revenues (exclusive of depreciation, shown separately below)	132,234	109,492	261,197	210,588
Other operating expenses:
Research and development	30,645	30,953	63,236	60,332
Selling, general and administrative	45,372	40,624	91,290	81,272
Depreciation	5,441	4,548	10,554	8,462
Restructuring and reorganization charges	1,826	3,329	1,941	4,229
Total operating expenses	215,518	188,946	428,218	364,883
Operating income	30,338	24,087	62,431	49,854
Other income (expense):
Interest expense	(4,498)	(4,480)	(9,058)	(8,746)
Amortization of original issue discount	(700)	(661)	(1,390)	(1,313)
Interest and investment income, net	417	770	936	1,581
Loss on extinguishment of debt				(810)
Other, net	1,280	1,008	(231)	362
Total other	(3,501)	(3,363)	(9,743)	(8,926)
Income before income taxes	26,837	20,724	52,688	40,928
Income tax provision	(7,458)	(5,607)	(14,058)	(11,797)
Net income	$ 19,379	$ 15,117	$ 38,630	$ 29,131
Weighted-average shares outstanding:
Basic	32,093	32,589	32,111	32,558
Diluted	32,458	32,908	32,448	33,005
Earnings per common share:
Basic	$ 0.60	$ 0.46	$ 1.20	$ 0.89
Diluted	$ 0.60	$ 0.46	$ 1.19	$ 0.88