Investments (Tables)

12 Months Ended

Apr. 30, 2018

Investments

Schedule of investments

	April 30,
	2018		2017
	(In thousands)
Short-term investments:
Held-to-maturity securities:
Municipal securities	$	35,344	$	47,437
U.S. government securities		31,620		14,515
Corporate bonds		46,685		55,519
Certificates of deposit		—		2,500
Total held-to-maturity and short-term investments	$	113,649	$	119,971
Long-term investments:
Held-to-maturity securities:
Municipal securities	$	2,046	$	8,942
U.S. government securities		27,356		22,540
Corporate bonds		9,112		8,117
Total held-to-maturity investments		38,514		39,599
Available-for-sale securities:
Auction rate securities		2,142		2,497
Total available-for-sale investments		2,142		2,497
Total long-term investments	$	40,656	$	42,096

Held to maturity securities

Investments

Schedule of amortized cost, gross unrealized gains, gross unrealized losses, and estimated fair value of 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):

	April 30, 2018								April 30, 2017
			Gross		Gross						Gross		Gross
	Amortized		Unrealized		Unrealized		Fair		Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value		Cost		Gains		Losses		Value
Municipal securities	$	37,390	$	9	$	(36)	$	37,363	$	56,379	$	30	$	(21)	$	56,388
U.S. government securities		58,976		—		(367)		58,609		37,055		2		(41)		37,016
Corporate bonds		55,797		2		(71)		55,728		63,636		9		(85)		63,560
Certificates of deposit		—		—		—		—		2,500		1		—		2,501
Total held-to-maturity investments	$	152,163	$	11	$	(474)	$	151,700	$	159,570	$	42	$	(147)	$	159,465

Schedule of amortized cost and fair value by contractual maturity

The amortized cost and fair value of the Company’s held‑to‑maturity securities by contractual maturity at April 30, 2018, are as follows:

	Cost		Fair Value
Due within one year	$	113,649	$	113,443
Due after one year through five years		38,514		38,257
Total	$	152,163	$	151,700

Available-for-sale securities | Auction rate securities

Investments

Schedule of amortized cost and fair value by contractual maturity

	April 30,
	2018		2017
Auction rate securities
Amortized cost	$	2,250	$	2,700
Gross unrealized losses		(108)		(203)
Fair value	$	2,142	$	2,497

The amortized cost and fair value of the Company’s auction rate securities by contractual maturity at April 30, 2018 are as follows (in thousands):

	Cost		Fair Value
Due after one through five years	$	250	$	252
Due after 10 years		2,000		1,890
Total	$	2,250	$	2,142

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,
	2018		2017
Auction rate securities
Amortized cost	$	2,250	$	2,700
Gross unrealized losses		(108)		(203)
Fair value	$	2,142	$	2,497