Fair Value of Financial Instruments (Tables)

9 Months Ended

12 Months Ended

Apr. 30, 2013

Jul. 31, 2012

Fair Value Disclosures [Abstract]

Schedule of Available-for-sale Securities Reconciliation [Table Text Block]

Available-for-sale investments within cash equivalents and investments consist of the following:

	April 30, 2013
	Amortized Cost		Unrealized Gains		Unrealized Losses			Estimated Fair Value
	(in thousands)
U.S. agency securities	$	31,120	$	21	$	—		$	31,141
Commercial paper	58,029		17		—			58,046
Corporate bonds	47,831		25		(8		)	47,848
Foreign government bonds	790		—		(3		)	787
Money market funds	42,021		—		—			42,021
Municipal debt securities	6,189		8		(2		)	6,195
Total	$	185,980	$	71	$	(13	)	$	186,038

	July 31, 2012
	Amortized Cost	Unrealized Gains	Unrealized Losses	Estimated Fair Value
	(in thousands)
Money market funds	105,107	—	—	105,107
Certificates of deposit	3,726	—	—	3,726
Total	108,833	—	—	108,833

Schedule of Unrealized Loss on Investments [Table Text Block]

The following table shows the gross unrealized losses and fair value of the Company's investments with unrealized losses, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position:

	As of April 30, 2013
	Less Than 12 Months					12 Months or Greater				Total
	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
	(in thousands)
Corporate bonds	$	10,074	$	(8	)	$	—	$	—	$	10,074	$	(8	)
Foreign government bonds	787		(3		)	—		—		787		(3		)
Municipal debt securities	1,098		(2		)	—		—		1,098		(2		)
Total	$	11,959	$	(13	)	$	—	$	—	$	11,959	$	(13	)

Investments Classified by Contractual Maturity Date

The following table summarizes the contractual maturities of the Company’s available-for-sale securities as of April 30, 2013:

	Expected maturities for the year ending July 31,
	2013		2014		2015		Total
	(in thousands)
U.S. agency securities	$	3,608	$	8,093	$	19,440	$	31,141
Commercial paper	46,266		11,780		—		58,046
Corporate bonds	3,501		38,054		6,293		47,848
Foreign government bonds	—		787		—		787
Money market funds	42,021		—		—		42,021
Municipal debt securities	—		1,886		4,309		6,195
Total	$	95,396	$	60,600	$	30,042	$	186,038

Fair Value, Assets Measured on Recurring Basis [Table Text Block]

	April 30, 2013
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets
Cash equivalents:
U.S. agency securities	$	—	$	1,683	$	—	$	1,683
Commercial paper	—		29,271		—		29,271
Money market funds	42,021		—		—		42,021
Short-term investments:
U.S. agency securities	—		6,466		—		6,466
Commercial paper	—		28,775		—		28,775
Corporate bonds	—		26,378		—		26,378
Foreign government bonds	—		787		—		787
Municipal debt securities	—		1,185		—		1,185
Long-term investments:
U.S. agency securities	—		22,992		—		22,992
Corporate bonds	—		21,470		—		21,470
Municipal debt securities	—		5,010		—		5,010
Total assets	$	42,021	$	144,017	$	—	$	186,038

The following table summarizes the Company's financial assets measured at fair value on a recurring basis, by level within the fair value hierarchy as of July 31, 2012:

	July 31, 2012
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets
Cash equivalents:
Money market funds	$	105,107	$	—	$	—	$	105,107
Certificates of deposit	3,726		—		—		3,726
Total assets	$	108,833	$	—	$	—	$	108,833