Fair Value Measurements (Tables)

9 Months Ended

Feb. 29, 2012

Fair Value Measurements

Schedule of fair value of financial instruments measured on a recurring basis

(In thousands)	As of February 29, 2012
	Level 1		Level 2		Level 3		Fair Value
Cash and cash equivalents	$	217,983	$	—	$	—	$	217,983
Marketable securities:
Canadian treasury securities	125,612		9,019		—		134,631
Total assets at fair value	$	343,595	$	9,019	$	—	$	352,614
Current accrued liabilities	$	—	$	31	$	—	$	31
Total liabilities at fair value	$	—	$	31	$	—	$	31

(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