Fair Value Measurements (Tables)

3 Months Ended

Aug. 31, 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 August 31, 2015
(In thousands)	Level 1		Level 2		Level 3		Fair Value
Cash and cash equivalents	$	146,860	$	—	$	—	$	146,860
Marketable securities:
Canadian treasury securities	—		53,354		—		53,354
Total assets at fair value	$	146,860	$	53,354	$	—	$	200,214

	As of May 31, 2015
(In thousands)	Level 1		Level 2		Level 3		Fair Value
Cash and cash equivalents	$	417,073	$	—	$	—	$	417,073
Marketable securities:
Canadian treasury securities	—		16,081		—		16,081
Total assets at fair value	$	417,073	$	16,081	$	—	$	433,154