4.	Marketable Securities:

The Company has evaluated its investment policies and determined that all of its investment securities are to be classified as available-for-sale. Available-for-sale securities are carried at fair value, with the unrealized gains and losses reported in Stockholders’ Equity under the caption “Accumulated other comprehensive loss.” Realized gains and losses on available-for-sale securities are included in “Other expense (income).” The Company records other-than-temporary impairment charges for its available-for-sale investments when it intends to sell the securities, it is more-likely-than not that it will be required to sell the securities before a recovery, or when it does not expect to recover the entire amortized cost basis of the securities. The cost of securities sold is based on the specific identification method.

The Company has determined that the gross unrealized losses on its marketable securities at December 31, 2017 and 2016 are temporary in nature. The Company reviews its investment portfolio to identify and evaluate investments that have indications of possible impairment. Factors considered in determining whether a loss is other-than-temporary include the length of time and extent to which fair value has been less than the cost basis, credit quality and the Company’s ability and intent to hold the investment for a period of time sufficient to allow for any anticipated recovery in market value.

At December 31, 2017 and 2016, marketable securities are categorized as follows:

	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Fair Value
December 31, 2017
Municipal notes and bonds	$	109,750	$	—	$	161	$	109,589
Total marketable securities	$	109,750	$	—	$	161	$	109,589
December 31, 2016
Municipal notes and bonds	$	87,088	$	6	$	65	$	87,029
Corporate bonds		842		1		—		843
Total marketable securities	$	87,930	$	7	$	65	$	87,872

The amortized cost and estimated fair value of marketable securities classified by the maturity date listed on the security, regardless of the Consolidated Balance Sheet classification, is as follows at December 31, 2017 and 2016:

	December 31, 2017				December 31, 2016
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due within one year	$	104,742	$	104,605	$	82,499	$	82,445
Due after one through five years		5,008		4,984		5,431		5,427
Due after five through ten years		—		—		—		—
Due after ten years		—		—		—		—
Total marketable securities	$	109,750	$	109,589	$	87,930	$	87,872

The following table summarizes the estimated fair value and gross unrealized holding losses of marketable securities, aggregated by investment instrument and period of time in an unrealized loss position, at December 31, 2017 and 2016.

	In Unrealized Loss Position For Less Than 12 Months				In Unrealized Loss Position For Greater Than 12 Months
	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
December 31, 2017
Municipal notes and bonds	$	98,805	$	161	$	—	$	—
Total marketable securities	$	98,805	$	161	$	—	$	—
December 31, 2016
Municipal notes and bonds	$	64,918	$	65	$	—	$	—
Total marketable securities	$	64,918	$	65	$	—	$	—

See Note 3 for additional discussion regarding the fair value of the Company’s marketable securities.