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, 2018	Aug. 31, 2017	Aug. 31, 2018	Aug. 31, 2017
Earnings Per Share [Abstract]
Net income	$ 16,746	$ 11,172	$ 45,061	$ 20,988
Weighted average shares outstanding (in shares)	45,130	48,071	45,730	48,342
Dilutive impact from common stock equivalents (in shares)	446	299	650	289
Diluted weighted average shares outstanding (in shares)	45,576	48,370	46,380	48,631
Basic earnings per share (in dollars per share)	$ 0.37	$ 0.23	$ 0.99	$ 0.43
Diluted earnings per share (in dollars per share)	$ 0.37	$ 0.23	$ 0.97	$ 0.43