Cash, Cash Equivalents and Marketable Securities Available-for-Sale (Tables)

6 Months Ended

Jun. 30, 2012

Cash, Cash Equivalents and Marketable Securities Available-for-Sale

Schedule of available-for-sale securities by major security type and class

			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
June 30, 2012	Cost		Gain		Loss		Value
U.S. Treasury securities	$	418,287	$	20	$	(90)	$	418,217
U.S. government-sponsored agency securities	67,377		49		(4)		67,422
U.S. government-sponsored agency MBS	130,425		591		(636)		130,380
Non-U.S. government, agency and Supranational securities	2,668		24		-		2,692
Corporate debt - global	79,454		509		(41)		79,922
Marketable equity securities	407		25		-		432
Total available-for-sale marketable securities	$	698,618	$	1,218	$	(771)	$	699,065

			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
December 31, 2011	Cost		Gain		Loss		Value
U.S. Treasury securities	$	228,996	$	58	$	(38)	$	229,016
U.S. government-sponsored agency securities	196,833		81		(69)		196,845
U.S. government-sponsored agency MBS	256,440		600		(1,901)		255,139
Non-U.S. government, agency and Supranational securities	2,666		19		-		2,685
Corporate debt - global	104,181		497		(233)		104,445
Marketable equity securities	407		153		-		560
Total available-for-sale marketable securities	$	789,523	$	1,408	$	(2,241)	$	788,690

Schedule of duration periods of available-for-sale debt securities

	Amortized		Fair
	Cost		Value
Duration of one year or less	$	200,221	$	200,280
Duration of one through three years	440,196		440,405
Duration of three through five years	57,794		57,948
Total	$	698,211	$	698,633