Investments (Tables)

12 Months Ended

Apr. 30, 2013

Investments

Schedule of investments

	April 30,
	2013		2012
	(In thousands)
Short-term investments:
Held-to-maturity securities:
Municipal securities	$	73,241	$	49,263
U.S. government securities		—		27,889
Total short-term investments	$	73,241	$	77,152
Long-term investments:
Held-to-maturity securities:
Municipal securities	$	54,158	$	52,261
Available-for-sale securities:
Auction rate securities		5,687		6,196
Convertible bonds		9,071		—
Total long-term investments	$	68,916	$	58,457

Schedule of amortized cost, gross unrealized gains, gross unrealized losses and estimated fair value of securities held-to-maturity investments

The amortized cost, gross unrealized losses, and estimated fair value of the held-to-maturity investments as of April 30, are as follows (in thousands):

	2013									2012
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Municipal securities	$	127,399	$	49	$	(23	)	$	127,425	$	101,524	$	48	$	(24	)	$	101,548
U.S. government securities		—		—		—			—		27,889		—		(1	)		27,888
Total held-to-maturity investments	$	127,399	$	49	$	(23	)	$	127,425	$	129,413	$	48	$	(25	)	$	129,436

Auction rate securities

Investments

Schedule of amortized cost, gross unrealized gains, gross unrealized losses and estimated fair value of available-for-sale investments

The amortized cost, gross unrealized losses, and estimated fair value of the available-for-sale auction rate securities are as follows (in thousands):

	April 30,
	2013			2012
Auction rate securities
Amortized cost	$	6,750		$	7,350
Gross unrealized losses		(1,063	)		(1,154	)
Fair value	$	5,687		$	6,196

Convertible bonds

Investments

Schedule of amortized cost, gross unrealized gains, gross unrealized losses and estimated fair value of available-for-sale investments

The amortized cost, gross unrealized gains, gross unrealized losses, and estimated fair value of the available-for-sale convertible bonds are as follows (in thousands):

	April 30,
	2013			2012
Convertible bonds
Amortized cost	$	3,037		$	—
Gross unrealized gains		6,173			—
Gross unrealized losses		(139	)		—
Fair value	$	9,071		$	—

Held-to-maturity securities

Investments

Schedule of amortized cost and fair value by contractual maturity

	Cost		Fair Value
Due within one year	$	73,241	$	73,258
Due after one year through five years		54,158		54,167
Total	$	127,399	$	127,425

Available-for-sale securities | Auction rate securities

Investments

Schedule of amortized cost and fair value by contractual maturity

The amortized cost and fair value of the Company's auction rate securities by contractual maturity at April 30, 2013 are as follows (in thousands):

	Cost		Fair Value
Due after five through 10 years	$	1,350	$	1,256
Due after 10 years		5,400		4,431
Total	$	6,750	$	5,687

Available-for-sale securities | Convertible bonds

Investments

Schedule of amortized cost and fair value by contractual maturity

The amortized cost and fair value of the Company's convertible bonds by contractual maturity at April 30, 2013 are as follows (in thousands):

	Cost		Fair Value
Due within five years	$	3,037	$	9,071
Total	$	3,037	$	9,071