Fair Value Measurements (Tables)

12 Months Ended

May 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 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

(In thousands)	As of May 31, 2011
	Level 1		Level 2		Level 3		Fair Value
Cash and cash equivalents	$	438,106	$	—	$	—	$	438,106
Marketable securities:
Canadian treasury securities	61,142		26,078		—		87,220
Total assets at fair value	$	499,248	$	26,078	$	—	$	525,326
Current accrued liabilities	$	—	$	869	$	—	$	869
Total liabilities at fair value	$	—	$	869	$	—	$	869