Selected Quarterly Information (Summary Of Selected Quarterly Information) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Selected Quarterly Information [Abstract]
Revenue	$ 115,294	$ 95,503	$ 103,518	$ 102,360	$ 89,253	$ 90,016	$ 82,246	$ 75,084	$ 416,675	$ 336,599	$ 264,013
Gross profit	72,720	53,692	63,121	62,344	53,205	55,026	50,986	48,648	251,877	207,865	173,076
Income (loss) from operations	3,704	(2,008)	3,234	5,564	(3,945)	1,943	(9,140)	8,562	10,494	(2,580)	41,819
Income (loss) before provision (benefit) for income taxes	3,239	(2,451)	3,331	6,694	(5,189)	4,208	(11,510)	6,294	10,813	(6,197)	47,415
Net income (loss)	$ (1,855)	$ 4,959	$ 2,273	$ 4,731	$ (4,693)	$ 3,139	$ (8,188)	$ 3,851	$ 10,108	$ (5,891)	$ 32,212
Net earnings (loss) per share, basic	$ (0.05)	$ 0.13	$ 0.06	$ 0.13					$ 0.27	$ (0.16)	$ 0.89
Net earnings (loss) per share, diluted	$ (0.05)	$ 0.13	$ 0.06	$ 0.12					$ 0.26	$ (0.16)	$ 0.85
Net earnings (loss) per share, basic and diluted					$ (0.13)	$ 0.08	$ (0.22)	$ 0.10