Fair Value Measurements (Tables)

3 Months Ended

Aug. 31, 2012

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: 

(In thousands)	As of August 31, 2012
	Level 1		Level 2		Level 3		Fair Value
Cash and cash equivalents	$	319,217	$	—	$	—	$	319,217
Marketable securities:
Canadian treasury securities	3,387		7,561		—		10,948
Total assets at fair value	$	322,604	$	7,561	$	—	$	330,165

(In thousands)	As of May 31, 2012
	Level 1		Level 2		Level 3		Fair Value
Cash and cash equivalents	$	339,825	$	—	$	—	$	339,825
Total assets at fair value	$	339,825	$	—	$	—	$	339,825