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 November 30, 2018 (in thousands):



	Amortized Cost		Unrealized Gains		Unrealized Losses			Estimated Fair Value
Current assets:
Cash	$	368,564	$	—	$	—		$	368,564
Cash equivalents:
Money market mutual funds	1,234,188		—		—			1,234,188
Time deposits	40,023		—		—			40,023
Total cash equivalents	1,274,211		—		—			1,274,211
Total cash and cash equivalents	1,642,775		—		—			1,642,775
Short-term fixed income securities:
Asset-backed securities	41,875		—		(367		)	41,508
Corporate debt securities	1,546,860		44		(24,696		)	1,522,208
Foreign government securities	4,179		—		(24		)	4,155
Municipal securities	18,601		1		(286		)	18,316
Total short-term investments	1,611,515		45		(25,373		)	1,586,187
Total cash, cash equivalents and short-term investments	$	3,254,290	$	45	$	(25,373	)	$	3,228,962

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 debt securities	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

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 November 30, 2018 and December 1, 2017 (in thousands):



	2018					2017
	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Corporate debt securities	$	538,109	$	(7,966	)	$	1,338,232	$	(5,459	)
Asset-backed securities	6,696		(54		)	64,618		(193		)
Municipal securities	6,599		(81		)	11,805		(115		)
Foreign government securities	—		—			2,388		(8		)
U.S. Treasury securities	—		—			593,296		(2,087		)
Total	$	551,404	$	(8,101	)	$	2,010,339	$	(7,862	)

There were 369 securities and 894 securities in an unrealized loss position for less than twelve months at November 30, 2018 and at December 1, 2017, 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 November 30, 2018 and December 1, 2017 (in thousands):



	2018					2017
	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Corporate debt securities	$	969,701	$	(16,730	)	$	500,689	$	(4,666	)
Asset-backed securities	34,812		(313		)	32,383		(210		)
Municipal securities	11,532		(205		)	598		(17		)
Foreign government securities	4,154		(24		)	—		—
U.S. Treasury securities	—		—			338,950		(1,465		)
Total	$	1,020,199	$	(17,272	)	$	872,620	$	(6,358	)

There were 577 securities and 360 securities in an unrealized loss position for more than twelve months at November 30, 2018 and at December 1, 2017, 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 November 30, 2018 (in thousands):



	Amortized Cost		Estimated Fair Value
Due within one year	$	615,867	$	612,104
Due between one and two years	574,554		564,199
Due between two and three years	289,033		282,144
Due after three years	132,061		127,740
Total	$	1,611,515	$	1,586,187

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 2018 and 2017, 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.