Income Taxes - Components of Income Tax Expense/(Benefit) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Feb. 28, 2015	Feb. 28, 2014	Feb. 28, 2015	Feb. 28, 2014
Income Tax Disclosure [Abstract]
Income (loss) before income tax expense (benefit)	$ (11,979)	$ 4,543	$ (7,732)	$ 3,630
Non taxable portion of revaluation of contingent consideration	9,229	5,000	9,229	5,000
Taxable portion of revaluation of contingent consideration	1,323	0	1,323	0
Morpheus product recall and discontinuance	(6,145)	0	(6,145)	0
Impairment of Automated Power Injector fixed asset	(8,200)	0	(8,200)	0
Impairment of indefinite-lived intangible asset	(6,400)	0	(6,400)	0
Ordinary income (loss) before income taxes	(1,786)	(457)	2,461	(1,370)
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount [Abstract]
Income tax expense / (benefit) based on ordinary income / (loss) at estimated tax rates	(461)	(233)	1,276	(587)
Discrete tax expense (benefit):
Morpheus product recall and discontinuance	(2,243)	0	(2,243)	0
Impairment of Automated Power Injector fixed asset	(2,993)	0	(2,993)	0
Taxable gain on revaluation of contingent consideration liability	483	0	483	0
Impairment of indefinite-lived intangible asset	(2,336)	0	(2,336)	0
Adjustment for elimination of the ASC 718 APIC pool	289	62	974	123
Retroactive renewal of the Research and Experimentation credit	(519)	0	(519)	0
Adjustment to fully reserved capital losses	0	43	0	43
Adjustments to prior period tax liabilities	63	156	80	170
Total income tax expense (benefit)	$ (7,717)	$ 28	$ (5,278)	$ (251)