Accumulated Other Comprehensive (Loss) Income - Changes in Accumulated Other Comprehensive (Loss) Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended						9 Months Ended
	Feb. 28, 2015	Nov. 30, 2014	Aug. 31, 2014	Feb. 28, 2014	Nov. 30, 2013	Aug. 31, 2013	Feb. 28, 2015	Feb. 28, 2014
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ 17,510	$ 26,818	$ 28,428	$ 40,286	$ 37,951	$ 38,123	$ 28,428	$ 38,123
Other comprehensive (loss) income before reclassifications	(22,261)	(9,796)	(2,098)	(5,222)	1,847	(660)
Amounts reclassified from accumulated other comprehensive (loss) income	488	488	488	488	488	488
Other comprehensive income (loss)	(21,773)	(9,308)	(1,610)	(4,734)	2,335	(172)	(32,691)	(2,571)
Ending Balance	(4,263)	17,510	26,818	35,552	40,286	37,951	(4,263)	35,552
Foreign Currency
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	29,632	39,410	41,525	52,706	50,666	51,312	41,525	51,312
Other comprehensive (loss) income before reclassifications	(22,237)	(9,778)	(2,115)	(5,121)	2,040	(646)
Amounts reclassified from accumulated other comprehensive (loss) income	0	0	0	0	0	0
Other comprehensive income (loss)	(22,237)	(9,778)	(2,115)	(5,121)	2,040	(646)
Ending Balance	7,395	29,632	39,410	47,585	52,706	50,666	7,395	47,585
Unrealized Loss on Derivatives
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(11,643)	(12,110)	(12,615)	(13,552)	(13,851)	(14,339)	(12,615)	(14,339)
Other comprehensive (loss) income before reclassifications	(29)	(21)	17	(102)	(189)	0
Amounts reclassified from accumulated other comprehensive (loss) income	488	488	488	488	488	488
Other comprehensive income (loss)	459	467	505	386	299	488
Ending Balance	(11,184)	(11,643)	(12,110)	(13,166)	(13,552)	(13,851)	(11,184)	(13,166)
Other
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(479)	(482)	(482)	1,132	1,136	1,150	(482)	1,150
Other comprehensive (loss) income before reclassifications	5	3	0	1	(4)	(14)
Amounts reclassified from accumulated other comprehensive (loss) income	0	0	0	0	0	0
Other comprehensive income (loss)	5	3	0	1	(4)	(14)
Ending Balance	$ (474)	$ (479)	$ (482)	$ 1,133	$ 1,132	$ 1,136	$ (474)	$ 1,133