Fair Value Measurements (Tables)

9 Months Ended

Feb. 28, 2018

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, 2018
(In thousands)	Level 1		Level 2		Level 3		Fair Value
Cash and cash equivalents	$	152,563	$	—	$	—	$	152,563
Marketable securities:
Canadian treasury securities	—		33,693		—		33,693
Total assets at fair value	$	152,563	$	33,693	$	—	$	186,256

	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