Goodwill (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Nov. 30, 2016	May 31, 2016	May 31, 2015
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 169,220	$ 166,414
Goodwill acquired (disposed) during the year	3,986	2,354
Adjustments to preliminary purchase price allocations	(19)	270
Foreign currency translation	(2,127)	182
Goodwill, ending balance	171,060	169,220
Services
Goodwill [Roll Forward]
Goodwill, beginning balance	119,683	117,279
Goodwill acquired (disposed) during the year	3,986	2,728
Adjustments to preliminary purchase price allocations	(19)	270
Foreign currency translation	(369)	(594)
Goodwill, ending balance	123,281	119,683
International
Goodwill [Roll Forward]
Goodwill, beginning balance	36,340	35,938
Goodwill acquired (disposed) during the year	0	(374)
Adjustments to preliminary purchase price allocations	0	0
Foreign currency translation	(1,758)	776
Goodwill, ending balance	34,582	36,340
Goodwill, cumulative impairment loss	9,900	9,900	$ 9,900
Products and Systems
Goodwill [Roll Forward]
Goodwill, beginning balance	13,197	13,197
Goodwill acquired (disposed) during the year	0	0
Adjustments to preliminary purchase price allocations	0	0
Foreign currency translation	0	0
Goodwill, ending balance	$ 13,197	$ 13,197