Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2018

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:

	Level 1				Level 2						Level 3				Total
(millions)	6/30/18		12/31/17		6/30/18			12/31/17			6/30/18		12/31/17		6/30/18			12/31/17
Cash equivalents	$	44	$	124	$	33		$	24		$	—	$	—	$	77		$	148
Equity mutual funds	6		6		—			—			—		—		6			6
Marketable securities:
Corporate debt securities	—		—		70			68			—		—		70			68
U.S. government and agency debt securities	—		—		1			6			—		—		1			6
Asset-backed debt securities	—		—		15			11			—		—		15			11
Certificates of deposit	—		—		9			13			—		—		9			13
Municipal debt securities	—		—		1			1			—		—		1			1
Derivative assets	—		—		7			2			—		—		7			2
Derivative liabilities	—		—		(18		)	(17		)	—		—		(18		)	(17		)