Investments - (Tables)

6 Months Ended

Jun. 30, 2019

Investments, Debt and Equity Securities [Abstract]

Amortized Cost, Gross Unrealized Gains and Losses, Fair Values of Investments

The amortized cost, gross unrealized gains, gross unrealized losses, and fair values of our investments as of June 30, 2019 and December 31, 2018 are presented below.

	June 30, 2019								December 31, 2018
(in millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Asset-backed securities	$	35	$	—	$	—	$	35	$	33	$	—	$	—	$	33
Corporate bonds	94		1		—		95		99		—		—		99
U.S. government agencies and government- sponsored agencies	5		—		—		5		7		—		—		7
U.S. treasuries	58		1		—		59		46		—		—		46
Exchange traded fund	1		—		—		1		1		—		—		1
Other debt securities	4		—		—		4		9		—		—		9
Total	$	197	$	2	$	—	$	199	$	195	$	—	$	—	$	195

Fair Value of Debt Investments by Contractual Maturity

The fair value of debt investments by contractual maturity are shown below:

(in millions)	June 30, 2019
One year or less	$	81
Over one year through five years	103
Over five years through ten years	7
Over ten years	7
Total fair value	$	198

Proceeds from available-for-sale securities

The gross proceeds from sales and maturities of AFS securities for the three and six months ended June 30, 2019 and June 30, 2018 are presented below. We had immaterial realized gains and losses from sales of investments for the three and six months ended June 30, 2019 and June 30, 2018.

	Three Months Ended June 30,				Six Months Ended June 30,
(in millions)	2019		2018		2019		2018
Gross proceeds from sales	$	14	$	—	$	28	$	39
Gross proceeds from maturities	19		10		36		24