Fair Value (Tables)

12 Months Ended

Dec. 31, 2012

Financial Assets Measured at Fair Value on Recurring Basis

The following table summarizes our fair value measurements at December 31, 2012 and 2011, respectively, for financial assets measured at fair value on a recurring basis:

			Fair Value Measurements Using
	Fair Value		Quoted Prices in Active Markets (Level 1)		Other Observable Inputs (Level 2)		Unobservable Inputs (Level 3)
	(in millions)
December 31, 2012
Cash equivalents	$	1,177	$	1,177	$	0	$	0
Debt securities:
U.S. Treasury and other U.S. government corporations and agencies:
U.S. Treasury and agency obligations		618		0		618		0
Mortgage-backed securities		1,603		0		1,603		0
Tax-exempt municipal securities		3,071		0		3,058		13
Mortgage-backed securities:
Residential		34		0		34		0
Commercial		659		0		659		0
Asset-backed securities		68		0		67		1
Corporate debt securities		3,794		0		3,770		24
Total debt securities		9,847		0		9,809		38
Total invested assets	$	11,024	$	1,177	$	9,809	$	38
December 31, 2011
Cash equivalents	$	1,205	$	1,205	$	0	$	0
Debt securities:
U.S. Treasury and other U.S. government corporations and agencies:
U.S. Treasury and agency obligations		725		0		725		0
Mortgage-backed securities		1,784		0		1,784		0
Tax-exempt municipal securities		2,856		0		2,840		16
Mortgage-backed securities:
Residential		44		0		44		0
Commercial		381		0		381		0
Asset-backed securities		83		0		82		1
Corporate debt securities		3,580		0		3,556		24
Total debt securities		9,453		0		9,412		41
Total invested assets	$	10,658	$	1,205	$	9,412	$	41

Changes in Fair Value of Assets Measured Using Significant Unobservable Inputs

During the years ended December 31, 2012, 2011, and 2010, the changes in the fair value of the assets measured using significant unobservable inputs (Level 3) were comprised of the following:

	For the years ended December 31,
	2012								2011									2010
	Private Placements/ Venture Capital		Auction Rate Securities			Total			Private Placements/ Venture Capital			Auction Rate Securities			Total			Private Placements/ Venture Capital			Auction Rate Securities			Total
	(in millions)
Beginning balance at January 1	$	25	$	16		$	41		$	14		$	52		$	66		$	24		$	69		$	93
Total gains or losses:
Realized in earnings		0		0			0			1			1			2			6			0			6
Unrealized in other comprehensive income		0		0			0			0			1			1			(4	)		2			(2	)
Purchases		0		0			0			17			0			17			3			0			3
Sales		0		(3	)		(3	)		(7	)		(38	)		(45	)		(13	)		(3	)		(16	)
Settlements		0		0			0			0			0			0			(2	)		(16	)		(18	)
Balance at December 31	$	25	$	13		$	38		$	25		$	16		$	41		$	14		$	52		$	66