Selected Quarterly Financial Data (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Nov. 30, 2013	Aug. 31, 2013	May 31, 2013	Feb. 28, 2013	Nov. 30, 2012	Aug. 31, 2012	May 31, 2012	Feb. 29, 2012	Nov. 30, 2013	Nov. 30, 2012	Nov. 30, 2011
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 90,980	$ 77,578	$ 81,705	$ 83,733	$ 86,642	$ 74,371	$ 74,128	$ 82,471	$ 333,996	$ 317,612	$ 333,610
Gross profit	82,885	69,059	73,216	73,854	76,980	64,883	65,518	73,917	299,014	281,298	296,833
Income from operations	23,900	9,661	14,386	15,793	18,659	11,289	12,800	25,041	63,740	67,789	108,712
Income from continuing operations	14,618	7,204	8,142	9,813	12,494	7,744	8,855	15,861	39,777	44,954	71,389
Net income (loss)	$ 15,036	$ 24,843	$ 3,910	$ 31,118	$ 36,025	$ 5,838	$ (1,908)	$ 7,489	$ 74,907	$ 47,444	$ 59,629
Continuing operations (in dollars per share)	$ 0.28	$ 0.13	$ 0.15	$ 0.17	$ 0.20	$ 0.12	$ 0.14	$ 0.26	$ 0.73	$ 0.71	$ 1.09
Continuing operations (in dollars per share)	$ 0.28	$ 0.13	$ 0.15	$ 0.17	$ 0.20	$ 0.12	$ 0.14	$ 0.25	$ 0.72	$ 0.71	$ 1.06