Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2012

Fair Value Measurements [Abstract]

Assets and liabilities measured at fair value on a recurring basis

	Quoted Prices in Active Markets for Identical Assets (Level 1)				Significant Other Observable Inputs (Level 2)						Significant Unobservable Inputs (Level 3)				Total
(millions)	3/31/12		12/31/11		3/31/12			12/31/11			3/31/12		12/31/11		3/31/12			12/31/11
Cash equivalents		257		128		27			31			-		-		284			159
Marketable securities:
Corporate debt securities		-		-		86			174			-		-		86			174
U.S. government and agency debt securities		-		-		12			32			-		-		12			32
Asset-backed debt securities		-		-		9			18			-		-		9			18
Certificates of deposit		-		-		16			35			-		-		16			35
Municipal debt securities		-		-		15			27			-		-		15			27
Derivative assets		-		-		3			4			-		-		3			4
Derivative liabilities		-		-		(9	)		(8	)		-		-		(9	)		(8	)