Fair Value Measurements (Tables)

9 Months Ended

Feb. 28, 2015

Fair Value Disclosures [Abstract]

Schedule of Fair Value of Financial Instruments Measured on a Recurring Basis

These financial instruments measured at fair value on a recurring basis are summarized below: 

	As of February 28, 2015
(In thousands)	Level 1		Level 2		Level 3		Fair Value
Cash and cash equivalents	$	358,320	$	—	$	—	$	358,320
Marketable securities:
Canadian treasury securities	—		44,874		—		44,874
Total assets at fair value	$	358,320	$	44,874	$	—	$	403,194
Current accrued liabilities	$	—	$	286	$	—	$	286
Total liabilities at fair value	$	—	$	286	$	—	$	286

	As of May 31, 2014
(In thousands)	Level 1		Level 2		Level 3		Fair Value
Cash and cash equivalents	$	513,288	$	—	$	—	$	513,288
Total assets at fair value	$	513,288	$	—	$	—	$	513,288
Current accrued liabilities	$	—	$	286	$	—	$	286
Total liabilities at fair value	$	—	$	286	$	—	$	286