Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2014

Fair Value Disclosures [Abstract]

Fair Value of Assets and Liabilities Measured on Recurring Basis

Our assets and liabilities that are measured at fair value on a recurring basis include the following (in millions):

			Fair Value Measurements at December 31, 2014 Using
	Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Money market funds	$	1,335	$	1,335	$	—	$	—
Fixed-income securities		38		—		38		—
Redeemable preferred stock		44		—		—		44
Foreign currency derivatives		28		—		28		—
Total assets	$	1,445	$	1,335	$	66	$	44

			Fair Value Measurements at December 31, 2013 Using
	Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Money market funds	$	99	$	99	$	—	$	—
Fixed-income securities		36		—		36		—
Redeemable preferred stock		25		—		—		25
Foreign currency derivatives		2		—		2		—
Total assets	$	162	$	99	$	38	$	25
Liabilities:
Interest rate derivatives	$	28	$	—	$	28	$	—
Electricity commodity derivatives(a)		3		—		3		—
Total liabilities	$	31	$	—	$	31	$	—

a) Our electricity commodity derivatives were associated with our Wheelabrator business and were divested in conjunction with the sale of that business in December 2014.