Earnings per share (Calculation of Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Aug. 31, 2020	Aug. 31, 2019	Aug. 31, 2020	Aug. 31, 2019
Earnings Per Share [Abstract]
Net income	$ 23,977	$ 13,557	$ 62,061	$ 31,140
Weighted average shares outstanding (in shares)	45,036	44,716	44,941	44,761
Dilutive impact from common stock equivalents (in shares)	328	587	441	531
Diluted weighted average shares outstanding (in shares)	45,364	45,303	45,382	45,292
Basic earnings per share (in dollars per share)	$ 0.53	$ 0.30	$ 1.38	$ 0.70
Diluted earnings per share (in dollars per share)	$ 0.53	$ 0.30	$ 1.37	$ 0.69