Fair Value Measurements (Tables)

3 Months Ended

Aug. 31, 2011

Fair Value Measurements

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

(In thousands)	As of August 31, 2011
	Level 1		Level 2		Level 3		Fair Value
Cash and cash equivalents	$	150,312	$	—	$	—	$	150,312
Marketable securities:
Canadian treasury securities	98,873		27,855		—		126,728
Total assets at fair value	$	249,185	$	27,855	$	—	$	277,040
Current accrued liabilities	$	—	$	548	$	—	$	548
Total liabilities at fair value	$	—	$	548	$	—	$	548

(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