CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS

Cash equivalents consist of instruments with remaining maturities of three months or less at the date of purchase. We classify all of our cash equivalents and short-term investments as “available-for-sale.” In general, these investments are free of trading restrictions. We carry these investments at fair value, based on quoted market prices or other readily available market information. Unrealized gains and losses, net of taxes, are included in accumulated other comprehensive income (loss), which is reflected as a separate component of stockholders’ equity in our Consolidated Balance Sheets. Gains and losses are recognized when realized in our Consolidated Statements of Income. When we have determined that an other-than-temporary decline in fair value has occurred, the amount of the decline that is related to a credit loss is recognized in income. Gains and losses are determined using the specific identification method.

Cash, cash equivalents and short-term investments consisted of the following as of December 1, 2017 (in thousands):



	Amortized Cost		Unrealized Gains		Unrealized Losses			Estimated Fair Value
Current assets:
Cash	$	280,488	$	—	$	—		$	280,488
Cash equivalents:
Money market mutual funds	2,006,741		—		—			2,006,741
Time deposits	18,843		—		—			18,843
Total cash equivalents	2,025,584		—		—			2,025,584
Total cash and cash equivalents	2,306,072		—		—			2,306,072
Short-term fixed income securities:
Asset-backed securities	98,403		1		(403		)	98,001
Corporate bonds and commercial paper	2,461,691		2,694		(10,125		)	2,454,260
Foreign government securities	2,396		—		(8		)	2,388
Municipal securities	21,189		8		(132		)	21,065
U.S. Treasury securities	941,538		2		(3,552		)	937,988
Total short-term investments	3,525,217		2,705		(14,220		)	3,513,702
Total cash, cash equivalents and short-term investments	$	5,831,289	$	2,705	$	(14,220	)	$	5,819,774

Cash, cash equivalents and short-term investments consisted of the following as of December 2, 2016 (in thousands):



	Amortized Cost		Unrealized Gains		Unrealized Losses			Estimated Fair Value
Current assets:
Cash	$	208,635	$	—	$	—		$	208,635
Cash equivalents:
Corporate bonds and commercial paper	1,249		—		—			1,249
Money market mutual funds	782,210		—		—			782,210
Municipal securities	1,301		—		—			1,301
Time deposits	17,920		—		—			17,920
Total cash equivalents	802,680		—		—			802,680
Total cash and cash equivalents	1,011,315		—		—			1,011,315
Short-term fixed income securities:
Asset backed securities	111,009		95		(190		)	110,914
Corporate bonds and commercial paper	2,464,769		3,135		(9,554		)	2,458,350
Municipal securities	134,710		37		(525		)	134,222
U.S. agency securities	39,538		42		—			39,580
U.S. Treasury securities	1,008,195		194		(1,470		)	1,006,919
Total short-term investments	3,758,221		3,503		(11,739		)	3,749,985
Total cash, cash equivalents and short-term investments	$	4,769,536	$	3,503	$	(11,739	)	$	4,761,300

See Note 4 for further information regarding the fair value of our financial instruments.

The following table summarizes the fair value and gross unrealized losses related to available-for-sale securities, aggregated by investment category, that have been in an unrealized loss position for less than twelve months, as of December 1, 2017 and December 2, 2016 (in thousands):



	2017					2016
	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Corporate bonds and commercial paper	$	1,338,232	$	(5,459	)	$	1,282,076	$	(9,474	)
Asset-backed securities	64,618		(193		)	54,063		(189		)
Municipal securities	11,805		(115		)	114,810		(525		)
Foreign government securities	2,388		(8		)	—		—
U.S. Treasury and agency securities	593,296		(2,087		)	580,529		(1,470		)
Total	$	2,010,339	$	(7,862	)	$	2,031,478	$	(11,658	)

There were 894 securities and 1,052 securities in an unrealized loss position for less than twelve months at December 1, 2017 and at December 2, 2016, respectively.

The following table summarizes the fair value and gross unrealized losses related to available-for-sale securities, aggregated by investment category, that were in a continuous unrealized loss position for more than twelve months, as of December 1, 2017 and December 2, 2016 (in thousands):



	2017					2016
	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Corporate bonds and commercial paper	$	500,689	$	(4,666	)	$	39,162	$	(80	)
Asset-backed security	32,383		(210		)	1,331		(1		)
Municipal securities	598		(17		)	—		—
U.S. Treasury securities	338,950		(1,465		)	—		—
Total	$	872,620	$	(6,358	)	$	40,493	$	(81	)

There were 360 securities and 23 securities in an unrealized loss position for more than twelve months at December 1, 2017 and at December 2, 2016, respectively.

The following table summarizes the cost and estimated fair value of short-term fixed income securities classified as short-term investments based on stated effective maturities as of December 1, 2017 (in thousands):



	Amortized Cost		Estimated Fair Value
Due within one year	$	1,025,894	$	1,023,639
Due between one and two years	1,294,919		1,289,307
Due between two and three years	815,254		812,828
Due after three years	389,150		387,928
Total	$	3,525,217	$	3,513,702

We review our debt and marketable equity securities classified as short-term investments on a regular basis to evaluate whether or not any security has experienced an other-than-temporary decline in fair value. We consider factors such as the length of time and extent to which the market value has been less than the cost, the financial condition and near-term prospects of the issuer and our intent to sell, or whether it is more likely than not we will be required to sell the investment before recovery of the investment’s amortized cost basis. If we believe that an other-than-temporary decline exists in one of these securities, we write down these investments to fair value. For debt securities, the portion of the write-down related to credit loss would be recorded to interest and other income, net in our Consolidated Statements of Income. Any portion not related to credit loss would be recorded to accumulated other comprehensive income (loss), which is reflected as a separate component of stockholders’ equity in our Consolidated Balance Sheets. For equity securities, the write-down would be recorded to investment gains (losses), net in our Consolidated Statements of Income. During fiscal 2017 and 2015, we did not consider any of our investments to be other-than-temporarily impaired. During fiscal 2016, we recorded immaterial other-than-temporary impairment losses associated with certain of our fixed income securities and wrote down the securities to fair value.