Computation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Feb. 29, 2012	Feb. 28, 2011
Basic and diluted:
Net income	$ 17,139	$ 21,435
Basic earnings per share denominator:
Weighted average shares outstanding	46,391,006	48,032,747
Basic earnings per share:
Net income	$ 0.37	$ 0.45
Diluted earnings per share denominator:
Weighted average shares outstanding	46,391,006	48,032,747
Common stock options	4,906	6,096
Diluted weighted average shares outstanding	46,395,912	48,038,843
Diluted earnings per share:
Net income	$ 0.37	$ 0.45
Anti-dilutive shares excluded in the computation of diluted earnings per share	243,960	269,241