Fair Value Measurements (Tables)

6 Months Ended

Nov. 30, 2017

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 November 30, 2017
(In thousands)	Level 1		Level 2		Level 3		Fair Value
Cash and cash equivalents	$	236,002	$	—	$	—	$	236,002
Marketable securities:
Canadian treasury securities	—		22,732		—		22,732
Total assets at fair value	$	236,002	$	22,732	$	—	$	258,734

	As of May 31, 2017
(In thousands)	Level 1		Level 2		Level 3		Fair Value
Cash and cash equivalents	$	169,266	$	—	$	—	$	169,266
Marketable securities:
Canadian treasury securities	—		22,219		—		22,219
Total assets at fair value	$	169,266	$	22,219	$	—	$	191,485