Quarterly report pursuant to Section 13 or 15(d)

Accumulated Other Comprehensive Income (Loss) (Details)

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Aug. 31, 2015	Aug. 31, 2014
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax, beginning balance	$ 311,761
Accumulated other comprehensive income (loss), net of tax, ending balance	305,702
Foreign currency translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax, beginning balance	(21,956)	$ (13,765)
Other comprehensive income before reclassifications	(2,511)	645
Amounts reclassified from accumulated other comprehensive loss to net income		0
Accumulated other comprehensive income (loss), net of tax, ending balance	(24,467)	(13,120)
Defined benefit pension plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax, beginning balance	(1,022)	(934)
Other comprehensive income before reclassifications	84	1
Amounts reclassified from accumulated other comprehensive loss to net income		5
Accumulated other comprehensive income (loss), net of tax, ending balance	(938)	(928)
AOCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax, beginning balance	(22,978)	(14,699)
Other comprehensive income before reclassifications	(2,427)	646
Amounts reclassified from accumulated other comprehensive loss to net income		5
Accumulated other comprehensive income (loss), net of tax, ending balance	$ (25,405)	$ (14,048)