Selected Quarterly Financial Data (Schedule Of Selected Quarterly Financial Data) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Selected Quarterly Financial Data [Abstract]
Consolidated revenue	$ 187,438	$ 166,944	$ 151,512	$ 147,758	$ 154,817	$ 135,717	$ 120,787	$ 102,079	$ 653,652	$ 513,400	$ 353,633
Gross profit	89,766	79,798	72,398	75,472	80,097	71,437	62,583	53,477	317,434	267,594	181,196
Total operating expenses	85,538	71,590	68,036	65,955	62,121	42,867	45,787	35,958	291,119	186,733	120,625
Income (loss) from operations	4,228	8,208	4,362	9,517	17,976	28,570	16,796	17,519	26,315	80,861	60,571
Income tax expense	75	1,113	694	3,559	5,248	8,279	4,791	1,569	5,441	19,887	4,338
Net income	$ 1,551	$ 3,084	$ 2,125	$ 4,877	$ 11,224	$ 17,640	$ 9,343	$ 5,883	$ 11,946	$ 44,119	$ 38,941
Basic and diluted net income per share	$ 0.01	$ 0.03	$ 0.02	$ 0.05	$ 0.11	$ 0.17	$ 0.10	$ 0.06	$ 0.11	$ 0.45	$ 0.48