Fair Value Measurements (Tables)

3 Months Ended

Aug. 31, 2013

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, 2013
	Level 1		Level 2		Level 3		Fair Value
Cash and cash equivalents	$	278,670	$	—	$	—	$	278,670
Marketable securities:
Canadian treasury securities	—		4,189		—		4,189
Total assets at fair value	$	278,670	$	4,189	$	—	$	282,859
Current accrued liabilities	$	—	$	107	$	—	$	107
Total liabilities at fair value	$	—	$	107	$	—	$	107

(In thousands)	As of May 31, 2013
	Level 1		Level 2		Level 3		Fair Value
Cash and cash equivalents	$	352,273	$	—	$	—	$	352,273
Marketable securities:
U.S. municipal bonds	—		5,680		—		5,680
Accounts receivable, net	—		39		—		39
Total assets at fair value	$	352,273	$	5,719	$	—	$	357,992