Selected Quarterly Financial Data (Correction of Prior Period Amounts) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Nov. 30, 2012	Aug. 31, 2012	May 31, 2012	Feb. 29, 2012	Nov. 30, 2011	Aug. 31, 2011	May 31, 2011	Feb. 28, 2011	Nov. 30, 2012	Nov. 30, 2011	Nov. 30, 2010
Income from continuing operations	$ 10,775	$ 5,353	$ 4,527	$ 11,949	$ 17,221	$ 14,426	$ 18,432	$ 16,263	$ 32,604	$ 66,342	$ 62,568
Net income	36,025	5,838	(1,908)	7,489	12,175	9,059	17,919	20,476	47,444	59,629	48,098
Continuing operations per share, basic (in dollars per share)	$ 0.17	$ 0.08	$ 0.07	$ 0.19	$ 0.27	$ 0.22	$ 0.28	$ 0.24	$ 0.52	$ 1.01	$ 0.98
Continuing operations per share, diluted (in dollars per share)	$ 0.17	$ 0.08	$ 0.07	$ 0.19	$ 0.27	$ 0.21	$ 0.27	$ 0.23	$ 0.51	$ 0.98	$ 0.94
As Previously Reported [Member]
Income from continuing operations					0	0	0	0		0	0
Net income					11,679	8,601	17,960	20,521		58,761	48,571
Continuing operations per share, basic (in dollars per share)					$ 0.00	$ 0.00	$ 0.00	$ 0.00		$ 0.00	$ 0.00
Continuing operations per share, diluted (in dollars per share)					$ 0.00	$ 0.00	$ 0.00	$ 0.00		$ 0.00	$ 0.00
Impact of Discontinued Operations [Member]
Income from continuing operations					16,725	13,968	18,473	16,308		65,474	62,812
Net income					0	0	0	0		0	0
Continuing operations per share, basic (in dollars per share)					$ 0.27	$ 0.21	$ 0.28	$ 0.24		$ 1.00	$ 0.98
Continuing operations per share, diluted (in dollars per share)					$ 0.26	$ 0.21	$ 0.27	$ 0.23		$ 0.97	$ 0.95
Adjustment [Member]
Income from continuing operations					496	458	(41)	(45)		868	(244)
Net income					$ 496	$ 458	$ (41)	$ (45)		$ 868	$ (473)
Continuing operations per share, basic (in dollars per share)					$ 0.01	$ 0.01	$ 0.00	$ 0.00		$ 0.01	$ 0.00
Continuing operations per share, diluted (in dollars per share)					$ 0.01	$ 0.01	$ 0.00	$ 0.00		$ 0.01	$ 0.00