3. Investments

Investments consist of the following (in thousands):


	October 27,		April 30,
	2018		2018
Short-term investments:
Held-to-maturity securities:
Municipal securities	$	14,326	$	35,344
U.S. government securities		36,948		31,620
Corporate bonds		82,262		46,685
Certificates of deposit		5,000		—
Total held-to-maturity and short-term investments	$	138,536	$	113,649
Long-term investments:
Held-to-maturity securities:
Municipal securities	$	993	$	2,046
U.S. government securities		26,746		27,356
Corporate bonds		2,720		9,112
Total held-to-maturity investments		30,459		38,514
Available-for-sale securities:
Auction rate securities		—		2,142
Total available-for-sale investments		—		2,142
Total long-term investments	$	30,459	$	40,656

Held-To-Maturity Securities

As of October 27, 2018 and April 30, 2018, the balance of held-to-maturity securities consisted of state and local government municipal securities, U.S. treasury securities, U.S. government-guaranteed agency securities, U.S. government-sponsored agency debt securities, highly rated corporate bonds, and certificates of deposit. Interest earned from these investments is recorded in interest income.

The amortized cost, gross unrealized gains, gross unrealized losses, and estimated fair value of the held-to-maturity investments as of October 27, 2018 were as follows (in thousands):


	October 27, 2018
			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
Municipal securities	$	15,319	$	—	$	(12)	$	15,307
U.S. government securities		63,694		3		(271)		63,426
Corporate bonds		84,982		2		(76)		84,908
Certificates of deposit		5,000		—		—		5,000
Total held-to-maturity investments	$	168,995	$	5	$	(359)	$	168,641

The amortized cost, gross unrealized gains, gross unrealized losses, and estimated fair value of the held-to-maturity investments as of April 30, 2018 were as follows (in thousands):


	April 30, 2018
			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
Municipal securities	$	37,390	$	9	$	(36)	$	37,363
U.S. government securities		58,976		—		(367)		58,609
Corporate bonds		55,797		2		(71)		55,728
Certificates of deposit		—		—		—		—
Total held-to-maturity investments	$	152,163	$	11	$	(474)	$	151,700

The amortized cost and fair value of the held-to-maturity securities by contractual maturity at October 27, 2018 were as follows (in thousands):


	Cost		Fair Value
Due within one year	$	138,536	$	138,270
Due after one year through five years		30,459		30,371
Total	$	168,995	$	168,641

Available-For-Sale Securities

Auction Rate Securities

As of April 30, 2018, the balance of available-for-sale auction rate securities consisted of two investment grade auction rate municipal bonds with maturities ranging from 1 to 16 years. These investments have characteristics similar to short term investments, because at predetermined intervals, generally ranging from 30 to 35 days, there is a new auction process at which the interest rates for these securities are reset to current interest rates. At the end of such period, the Company chooses to roll over its holdings or redeem the investments for cash. A market maker facilitates the redemption of the securities and the underlying issuers are not required to redeem the investment within 365 days. Interest earned from these investments is recorded in interest income.

During the three months ended July 28, 2018, the remaining investment grade auction rate municipal bonds were redeemed at par value.

The amortized cost, gross unrealized gains, gross unrealized losses, and estimated fair value of the auction rate securities as of April 30, 2018, were as follows (in thousands):


			Gross		Gross
	Amortized		Unrealized		Unrealized
	Cost		Gains		Losses		Fair Value
Auction rate securities	$	2,250	$	—	$	(108)	$	2,142
Total available-for-sale investments	$	2,250	$	—	$	(108)	$	2,142