Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2014

Fair Value Disclosures [Abstract]

Assets and liabilities measured at fair value on a recurring basis

	December 31, 2014
	Quoted prices in active markets for identical assets		Significant other observable inputs		Significant other unobservable inputs
	Level 1		Level 2		Level 3		Total
			(millions)
Assets at fair value:
Derivative financial instruments	—		26		—		26
Total assets	$	—	$	26	$	—	$	26
Liabilities at fair value:
Derivative financial instruments	$	—	$	21	$	—	$	21
Total liabilities	$	—	$	21	$	—	$	21

	December 31, 2013
	Quoted prices in active markets for identical assets		Significant other observable inputs		Significant other unobservable inputs
	Level 1		Level 2		Level 3		Total
			(millions)
Assets at fair value:
Derivative financial instruments	—		23		—		23
Total assets	$	—	$	23	$	—	$	23
Liabilities at fair value:
Derivative financial instruments	$	—	$	2	$	—	$	2
Total liabilities	$	—	$	2	$	—	$	2

Summary of the estimated fair value of the company's financial instruments held or issued to finance the company's operations

	December 31,
	2014				2013
	Carrying amount		Fair value		Carrying amount		Fair value
			(millions)
Assets:
Cash and cash equivalents	$	635	$	635	$	796	$	796
Fiduciary funds (included within Fiduciary assets)	$	1,888	$	1,888	$	1,662	$	1,662
Liabilities:
Current portion of long-term debt	$	167	$	169	$	15	$	15
Long-term debt	2,142		2,327		2,311		2,444