Investments (Tables)

12 Months Ended

Dec. 31, 2018

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 December 31, 2018 and December 31, 2017 are presented below:



	December 31, 2018
(in millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Asset-backed securities	$	33	$	—	$	—	$	33
Corporate bonds	99		—		—		99
U.S. government agencies and government-sponsored agencies	7		—		—		7
U.S. treasuries	46		—		—		46
Exchange traded fund	1		—		—		1
Other debt securities	9		—		—		9
Total	$	195	$	—	$	—	$	195



	December 31, 2017
(in millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
U.S. treasuries	$	37	$	—	$	—	$	37
Exchange traded fund	1		—		—		1
Total	$	38	$	—	$	—	$	38

Investments with a Continuous Unrealized Loss Position

Investments in a continuous unrealized loss position as of December 31, 2018 and December 31, 2017 are presented below.



	December 31, 2018
	Less than 12 months				12 months or more				Total
(in millions)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Asset-backed securities	$	25	$	—	$	—	$	—	$	25	$	—
Corporate bonds	84		—		—		—		84		—
U.S. government agencies and government-sponsored agencies	4		—		—		—		4		—
U.S. treasuries	21		—		—		—		21		—
Other debt securities	7		—		—		—		7		—
Total	$	141	$	—	$	—	$	—	$	141	$	—



	December 31, 2017
	Less than 12 months				12 months or more				Total
(in millions)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
U.S. treasuries	$	5	$	—	$	24	$	—	$	29	$	—
Total	$	5	$	—	$	24	$	—	$	29	$	—

Fair Value of Debt Investments by Contractual Maturity

Actual maturities may differ from contractual maturities because borrowers may have the right to prepay obligations with or without prepayment penalties.

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



	December 31, 2018
(in millions)	One year or less		Over One Year Through Five Years		Over Five Years Through Ten Years		Over Ten Years		Fair Value
Asset-backed securities	$	4	$	26	$	3	$	—	$	33
Corporate bonds	42		57		—		—		99
U.S. government agencies and government-sponsored agencies	1		2		—		4		7
U.S. treasuries	12		34		—		—		46
Other debt securities	—		1		—		8		9
Total	$	59	$	120	$	3	$	12	$	194



	December 31, 2017
(in millions)	One year or less		Over One Year Through Five Years		Over Five Years Through Ten Years		Over Ten Years		Fair Value
U.S. treasuries	$	—	$	37	$	—	$	—	$	37
Total	$	—	$	37	$	—	$	—	$	37

Proceeds from Available-for-sale Securities

The gross proceeds from sales and maturities of AFS securities for the years ended December 31, 2018, 2017 and 2016 are shown below. We had immaterial gross realized gains and losses from sales of investments for the years ended December 31, 2018, 2017 and 2016.



	Year Ended December 31,
(in millions)	2018		2017		2016
Gross proceeds from sales	$	54	$	—	$	—
Gross proceeds from maturities	47		14		28
Total	$	101	$	14	$	28