Earnings per share (Calculation of Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	May 31, 2018	May 31, 2017	May 31, 2018	May 31, 2017
Earnings Per Share [Abstract]
Net income	$ 15,403	$ 10,341	$ 28,315	$ 9,816
Weighted average shares outstanding (in shares)	45,531	48,221	46,030	48,477
Dilutive impact from common stock equivalents (in shares)	556	269	751	285
Diluted weighted average shares outstanding (in shares)	46,087	48,490	46,781	48,762
Basic earnings per share (in dollars per share)	$ 0.34	$ 0.21	$ 0.62	$ 0.20
Diluted earnings per share (in dollars per share)	$ 0.33	$ 0.21	$ 0.61	$ 0.20