INVESTMENTS

The Company classifies the marketable securities in which it invests as available-for-sale securities. These securities are measured at fair value in the financial statements with unrealized gains or losses recorded in Other comprehensive income in the Company's Consolidated Statements of Comprehensive Income (Loss). At the time the securities are sold or otherwise disposed of, gross realized gains and losses are included in Net income (loss) Gross realized gains and losses are based on the carrying value (cost, net of discounts or premiums) of the sold investment. The amounts reclassified out of Other comprehensive income during the three and six months ended June 30, 2016 and 2015 were insignificant.

The amortized cost, gross unrealized gains, gross unrealized losses, and fair value of available-for-sale investment securities by major security type and class of security at June 30, 2016 and December 31, 2015 were as follows:



		Investments
(In thousands)		Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
2016
	Federal agency notes	$	279,850	$	259	$	(46	)	$	280,063
	Commercial paper	31,935		39		—			31,974
	Subtotal	311,785		298		(46		)	312,037
	Mutual funds	704		274		—			978
	Total	$	312,489	$	572	$	(46	)	$	313,015

2015
	Federal agency notes	$	285,276	$	—	$	(519	)	$	284,757
	Commercial paper	31,730		—		(58		)	31,672
	Subtotal	317,006		—		(577		)	316,429
	Mutual funds	482		261		—			743
	Total	$	317,488	$	261	$	(577	)	$	317,172

The mutual funds included in the investment table above are included in Other noncurrent assets on the Company's Consolidated Balance Sheets. Included in the investments balance at June 30, 2016 and December 31, 2015 is $18.5 million which has been reserved as collateral on the Company's undrawn letters of credit of approximately $17.5 million.

The maturities of available-for-sale securities at June 30, 2016 were as follows:



(In thousands)	Amortized cost		Fair value
Federal agency notes
Due in one year or less	$	214,745	$	214,821
Due after one year through two years	65,105		65,242
Total	$	279,850	$	280,063

Commercial paper
Due in one year or less	$	16,485	$	16,488
Due after one year through two years	15,450		15,486
Total	$	31,935	$	31,974

The Company has long-term investments in various Canadian junior exploration companies, recorded on the Company's Consolidated Balance Sheets at cost. The Company sold its investment in Marathon Gold in the second quarter of 2016 and recorded a gain of $0.5 million. The Company determined there was no impairment for the remaining long-term investments for the three and six months ended June 30, 2016. For the three and six months ended June 30, 2015, the Company determined that certain of its remaining long-term investments were other than temporarily impaired and recorded a loss of less than $0.1 million. These long-term investments totaled approximately $0.1 million at June 30, 2016 and $0.5 million at December 31, 2015, and are recorded in Other noncurrent assets on the Company's Consolidated Balance Sheets.