Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2015

Fair Value Disclosures [Abstract]

Assets and liabilities measured at fair value on a recurring basis

Our assets and liabilities measured at fair value on a recurring basis were as follows:

	Quoted Prices in Active Markets for Identical Assets (Level 1)				Significant Other Observable Inputs (Level 2)						Significant Unobservable Inputs (Level 3)				Total
(millions)	6/30/15		12/31/14		6/30/15			12/31/14			6/30/15		12/31/14		6/30/15			12/31/14
Cash equivalents	$	129	$	93	$	19		$	32		$	—	$	—	$	148		$	125
Equity mutual funds	4		4		—			—			—		—		4			4
Marketable securities:
Corporate debt securities	—		—		57			93			—		—		57			93
U.S. government and agency debt securities	—		—		2			22			—		—		2			22
Asset-backed debt securities	—		—		12			17			—		—		12			17
Certificates of deposit	—		—		9			18			—		—		9			18
Municipal debt securities	—		—		2			4			—		—		2			4
Derivative assets	—		—		5			4			—		—		5			4
Derivative liabilities	—		—		(21		)	(26		)	—		—		(21		)	(26		)