Fair Value Measurements (Tables)

6 Months Ended

Nov. 30, 2011

Fair Value Measurements

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

(In thousands)	As of November 30, 2011
	Level 1	Level 2		Level 3		Fair Value
Cash and cash equivalents	$  207,772	$	—	$	—	$	207,772
Marketable securities:
Canadian treasury securities	121,829	8,004		—		129,833
Accounts receivable, net	—	31		—		31
Total assets at fair value	$  329,601	$	8,035	$	—	$	337,636
Current accrued liabilities	$           —	$	511	$	—	$	511
Total liabilities at fair value	$           —	$	511	$	—	$	511

(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