Financial Instruments and Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2018

Investments, Debt and Equity Securities [Abstract]

Summary of Financial Instruments by Significant Categories and Fair Value Measurement on a Recurring Basis

The following table summarizes our financial instruments by significant categories and fair value measurement on a recurring basis as of September 30, 2018 and December 31, 2017.

(in millions)	Level 1		Level 2		Total
September 30, 2018
Cash equivalents:
Money market funds	$	3	$	—	$	3
Total cash equivalents	3		—		3
Investments:
Asset-backed securities	—		35		35
Corporate bonds	—		86		86
U.S. government agencies and government-sponsored agencies	—		8		8
U.S. treasuries	—		29		29
Other debt securities	—		10		10
Total investments	—		168		168
Restricted cash equivalents:
Money market mutual funds	241		—		241
Commercial paper	20		—		20
Total restricted cash equivalents	261		—		261
Restricted investments:
U.S. treasuries	—		5		5
Exchange traded fund	1		—		1
Certificate of deposit	—		2		2
Total restricted investments	1		7		8
Total investments and restricted cash equivalents and investments	$	265	$	175	$	440
December 31, 2017
Restricted cash equivalents:
Money market mutual funds	$	199	$	—	$	199
Commercial paper	21		—		21
Total restricted cash equivalents	220		—		220
Restricted investments:
U.S. treasuries	37		—		37
Exchange traded fund	1		—		1
Certificate of deposit	—		2		2
Total restricted investments	38		2		40
Total restricted cash equivalents and investments	$	258	$	2	$	260