4. Marketable Securities

During all periods shown, marketable securities are classified as available-for-sale. The amortized cost, gross unrealized gains (losses) and fair values of available-for-sale securities by major security type and class of security as of January 31, 2018 and 2017 are as follows:

	Amortized Cost		Unrealized Gains		Unrealized (Losses)			Fair Value
As of January 31, 2018
Short-term Investments:
Corporate bonds	$	111,612	$	—	$	(184	)	$	111,428
Municipal and pre-refunded municipal bonds		52,474		11		(39	)		52,446
Certificates of deposit		1,251		—		—			1,251
		165,337		11		(223	)		165,125
Long-term Investments:
Corporate bonds		39,853		—		(228	)		39,625
Municipal and pre-refunded municipal bonds		9,873		8		(24	)		9,857
Mutual funds, held in rabbi trust		5,973		274		(10	)		6,237
Certificates of deposit		2,969		—		—			2,969
		58,668		282		(262	)		58,688
	$	224,005	$	293	$	(485	)	$	223,813
As of January 31, 2017
Short-term Investments:
Corporate bonds	$	59,403	$	7	$	(90	)	$	59,320
Municipal and pre-refunded municipal bonds		51,731		28		(12	)		51,747
		111,134		35		(102	)		111,067
Long-term Investments:
Corporate bonds		19,102		9		(33	)		19,078
Municipal and pre-refunded municipal bonds		19,488		35		(9	)		19,514
Mutual funds, held in rabbi trust		4,583		91		(1	)		4,673
Certificates of deposit		1,023		—		—			1,023
		44,196		135		(43	)		44,288
	$	155,330	$	170	$	(145	)	$	155,355

Proceeds from the sales and maturities of available-for-sale securities were $243,818, $243,159 and $374,057 in fiscal 2018, 2017 and 2016, respectively. The Company included in “Interest income,” in the Consolidated Statements of Income, a net realized loss of $35 during fiscal 2018, a net realized loss of $83 during fiscal 2017 and a net realized gain of $43 during fiscal 2016. Amortization of discounts and premiums, net, resulted in a reduction of “Interest income” of $2,588, $2,200 and $3,841 for fiscal years 2018, 2017 and 2016, respectively. Mutual funds represent assets held in an irrevocable rabbi trust for the Company’s Non-qualified Deferred Compensation Plan (“NQDC”). These assets are a source of funds to match the funding obligations to participants in the NQDC but are subject to the Company’s general creditors. The Company elected the fair value option for financial assets for the mutual funds held in the rabbi trust resulting in all unrealized gains and losses being recorded in “Interest income” in the Consolidated Statements of Income.

The following tables show the gross unrealized losses and fair value of the Company’s marketable securities with unrealized losses that are not deemed to be other-than-temporarily impaired aggregated by the length of time that individual securities have been in a continuous unrealized loss position, at January 31, 2018 and January 31, 2017, respectively.

	January 31, 2018
	Less Than 12 Months					12 Months or Greater				Total
Description of Securities	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Corporate bonds	$	151,053	$	(412	)	$	—	$	—	$	151,053	$	(412	)
Municipal and pre-refunded municipal bonds		39,671		(63	)		—		—		39,671		(63	)
Mutual funds, held in rabbi trust		474		(10	)		—		—		474		(10	)
Total	$	191,198	$	(485	)	$	—	$	—	$	191,198	$	(485	)

	January 31, 2017
	Less Than 12 Months					12 Months or Greater				Total
Description of Securities	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Corporate bonds	$	61,612	$	(123	)	$	—	$	—	$	61,612	$	(123	)
Municipal and pre-refunded municipal bonds		18,713		(21	)		—		—		18,713		(21	)
Mutual funds, held in rabbi trust		316		(1	)		—		—		316		(1	)
Total	$	80,641	$	(145	)	$	—	$	—	$	80,641	$	(145	)

As of January 31, 2018 and 2017, there were a total of 336 and 206 securities with unrealized loss positions within the Company’s portfolio, respectively.