3.	AVAILABLE-FOR-SALE SECURITIES

The following table is a summary of available-for-sale debt and equity securities recorded in cash and cash equivalents or marketable securities in our Consolidated Balance Sheets. Estimated fair values of available-for-sale securities are generally based on prices obtained from commercial pricing services (in thousands):

 

		Amortized Cost				Gross Unrealized Gains				Gross Unrealized Losses				Estimated Fair Value
December 31, 2011
Debt securities:
U.S. treasury securities		$	—			$	—			$	—			$	—
Money market funds			7,455,982				—				—				7,455,982
Certificates of deposit			1,140,000				—				(18	)			1,139,982
U.S. government agencies and FDIC guaranteed securities			—				—				—				—
Municipal debt securities			—				—				—				—
Non-U.S. government securities			55,246				—				(30,505	)			24,741
Corporate debt securities			404,994				—				(5	)			404,989
Residential mortgage and asset-backed securities			—				—				—				—
Student loan-backed securities			51,500				—				(4,548	)			46,952
Total debt securities			9,107,722				—				(35,076	)			9,072,646
Equity securities			1,451				7,052				—				8,503
Total		$	9,109,173			$	7,052			$	(35,076	)		$	9,081,149
December 31, 2010
Debt securities:
U.S. treasury securities		$	1,349,348			$	7,109			$	(1,020	)		$	1,355,437
Money market funds			520,063				—				—				520,063
Certificates of deposit			127,594				41				(16	)			127,619
U.S. government agencies and FDIC guaranteed securities			1,284,654				11,919				(463	)			1,296,110
Municipal debt securities			17,543				103				(21	)			17,625
Non-U.S. government securities			286,410				1,880				(86	)			288,204
Corporate debt securities			985,382				7,999				(1,746	)			991,635
Residential mortgage and asset-backed securities			277,359				923				(1,239	)			277,043
Student loan-backed securities			75,900				—				(5,129	)			70,771
Total debt securities			4,924,253				29,974				(9,720	)			4,944,507
Equity securities			1,451				3,180				—				4,631
Total		$	4,925,704			$	33,154			$	(9,720	)		$	4,949,138

The following table summarizes the classification of the available-for-sale debt and equity securities on our Consolidated Balance Sheets (in thousands):

 

		December 31, 2011				December 31, 2010
Cash and cash equivalents		$	9,000,954			$	538,946
Short-term marketable securities			16,491				1,190,789
Long-term marketable securities			63,704				3,219,403
Total		$	9,081,149			$	4,949,138

 

The following table summarizes our portfolio of available-for-sale debt securities by contractual maturity (in thousands):

 

		December 31, 2011								December 31, 2010
		Amortized Cost				Fair Value				Amortized Cost				Fair Value
Less than one year		$	1,574,140			$	1,561,462			$	1,726,095			$	1,729,735
Greater than one year but less than five years			26,100				8,249				3,022,744				3,044,114
Greater than five years but less than ten years			—				—				33,076				33,580
Greater than ten years			7,507,482				7,502,935				142,338				137,078
Total		$	9,107,722			$	9,072,646			$	4,924,253			$	4,944,507

The following table summarizes the gross realized gains and losses related to sales of marketable securities (in thousands):

 

		Year Ended December 31,
		2011				2010				2009
Gross realized gains on sales		$	42,849			$	13,254			$	10,373
Gross realized losses on sales		$	(12,526	)		$	(3,657	)		$	(1,405	)

The cost of securities sold was determined based on the specific identification method.

The following table summarizes our available-for-sale debt securities that were in a continuous unrealized loss position, but were not deemed to be other-than-temporarily impaired (in thousands):

 

		Less Than 12 Months								12 Months or Greater								Total
		Gross Unrealized Losses				Estimated Fair Value				Gross Unrealized Losses				Estimated Fair Value				Gross Unrealized Losses				Estimated Fair Value
December 31, 2011
Debt securities:
U.S. treasury securities		$	—			$	—			$	—			$	—			$	—			$	—
U.S. government agencies and FDIC guaranteed securities			—				—				—				—				—				—
Municipal debt securities			—				—				—				—				—				—
Non-U.S. government securities			(30,505	)			24,741				—				—				(30,505	)			24,741
Corporate debt securities			(5	)			224,989				—				—				(5	)			224,989
Certificates of deposit			(18	)			1,019,982				—				—				(18	)			1,019,982
Residential mortgage and asset-backed securities			—				—				—				—				—				—
Student loan-backed securities			—				—				(4,548	)			46,952				(4,548	)			46,952
Total		$	(30,528	)		$	1,269,712			$	(4,548	)		$	46,952			$	(35,076	)		$	1,316,664
December 31, 2010
Debt securities:
U.S. treasury securities		$	(1,020	)		$	531,184			$	—			$	—			$	(1,020	)		$	531,184
Certificates of deposit			(13	)			39,987				—				—				(13	)			39,987
U.S. government agencies and FDIC guaranteed securities			(463	)			226,176				—				—				(463	)			226,176
Municipal debt securities			(21	)			4,688				—				—				(21	)			4,688
Non-U.S. government securities			(86	)			44,317				—				—				(86	)			44,317
Corporate debt securities			(1,749	)			419,425				—				—				(1,749	)			419,425
Residential mortgage and asset-backed securities			(1,239	)			197,330				—				—				(1,239	)			197,330
Student loan-backed securities			—				—				(5,129	)			70,771				(5,129	)			70,771
Total		$	(4,591	)		$	1,463,107			$	(5,129	)		$	70,771			$	(9,720	)		$	1,533,878

 

As of December 31, 2011 and 2010, approximately 36% and 34%, respectively, of the total number of securities were in an unrealized loss position. The gross unrealized losses for Greek government-issued bonds reflect a higher discount rate used in the valuation of these securities as compared to the implied interest rates of these securities resulting primarily from lack of market activity and liquidity of the underlying securities. The gross unrealized losses for auction rate securities also reflect a higher discount rate used in the valuation of these securities. Based on our review of these securities, we believe we had no other-than-temporary impairments on these securities as of December 31, 2011 and 2010 because we do not intend to sell these securities and it is not more likely than not that we will be required to sell these securities before the recovery of their amortized cost basis.