Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	May. 31, 2015	May. 31, 2014	May. 31, 2013
Changes in the carrying amount of goodwill
Balance at the beginning of the period	$ 130,516	$ 115,270
Goodwill acquired during the year	43,466	15,790
Adjustments to preliminary purchase price allocations	3,162	(2,329)
Foreign currency translation	(10,730)	1,785
Balance at the end of the period	166,414	130,516	$ 115,270
Goodwill impairment	0	0	9,938
Goodwill, cumulative impairment charge	9,900
Brazil
Changes in the carrying amount of goodwill
Goodwill impairment			9,900
Services
Changes in the carrying amount of goodwill
Balance at the beginning of the period	73,767	61,285
Goodwill acquired during the year	41,986	15,558
Adjustments to preliminary purchase price allocations	3,529	(2,769)
Foreign currency translation	(2,003)	(307)
Balance at the end of the period	117,279	73,767	61,285
International
Changes in the carrying amount of goodwill
Balance at the beginning of the period	43,552	40,788
Goodwill acquired during the year	1,480	232
Adjustments to preliminary purchase price allocations	(367)	440
Foreign currency translation	(8,727)	2,092
Balance at the end of the period	35,938	43,552	40,788
Products
Changes in the carrying amount of goodwill
Balance at the beginning of the period	13,197	13,197
Adjustments to preliminary purchase price allocations		0
Balance at the end of the period	$ 13,197	$ 13,197	$ 13,197