Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Measurements

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 as of December 31 (in millions):

			Fair Value Measurements Using
			Quoted		Significant
			Prices in		Other		Significant
			Active		Observable		Unobservable
			Markets		Inputs		Inputs
	Total		(Level 1)		(Level 2)		(Level 3)
2017
Assets:
Money market funds	$	225	$	225	$	—	$	—
Available-for-sale securities		49		—		49		—
Fixed-income securities		47		—		47		—
Redeemable preferred stock		55		—		—		55
Total assets	$	376	$	225	$	96	$	55
2016
Assets:
Money market funds	$	35	$	35	$	—	$	—
Available-for-sale securities		46		—		46		—
Fixed-income securities		39		—		39		—
Redeemable preferred stock		54		—		—		54
Total assets	$	174	$	35	$	85	$	54