Investments (Tables)

3 Months Ended

Mar. 31, 2020

Investments, Debt and Equity Securities [Abstract]

Available-for-Sale Investments

The following tables summarize our investments as of the dates indicated:

	March 31, 2020
	Amortized		Gross Unrealized				Estimated Fair
	Cost		Gains		Losses		Value
	(In millions)
Corporate debt securities	$	1,277	$	4	$	21	$	1,260
Mortgage-backed securities	453		6		8		451
Asset-backed securities	144		—		1		143
Municipal securities	138		—		—		138
Certificates of deposit	7		—		—		7
GSEs	6		—		—		6
U.S. Treasury notes	5		—		—		5
Totals	$	2,030	$	10	$	30	$	2,010

	December 31, 2019
	Amortized		Gross Unrealized				Estimated Fair
	Cost		Gains		Losses		Value
	(In millions)
Corporate debt securities	$	1,174	$	5	$	1	$	1,178
Mortgage-backed securities	420		1		1		420
Asset-backed securities	126		1		—		127
Municipal securities	78		—		—		78
Certificates of deposit	1		—		—		1
GSEs	49		—		—		49
U.S. Treasury notes	86		—		—		86
Foreign securities	7		—		—		7
Totals	$	1,941	$	7	$	2	$	1,946

Contractual Maturities of Investments

The contractual maturities of our available-for-sale investments as of March 31, 2020 are summarized below:

	Amortized Cost		Estimated Fair Value
	(In millions)
Due in one year or less	$	375	$	375
Due after one year through five years	1,032		1,017
Due after five years through ten years	183		181
Due after ten years	440		437
Totals	$	2,030	$	2,010

Available-for-Sale Investments in a Continuous Loss Position

The following table segregates those available-for-sale investments that have been in a continuous loss position for less than 12 months, and those that have been in a continuous loss position for 12 months or more as of March 31, 2020:

	In a Continuous Loss Position for Less than 12 Months					In a Continuous Loss Position for 12 Months or More
	Estimated Fair Value		Unrealized Losses		Total Number of Positions	Estimated Fair Value		Unrealized Losses		Total Number of Positions
	(Dollars in millions)
Corporate debt securities	$	805	$	21	627	$	—	$	—	—
Mortgage-backed securities	211		8		128	—		—		—
Asset-backed securities	90		1		70	—		—		—
Totals	$	1,106	$	30	825	$	—	$	—	—

The following table segregates those available-for-sale investments that have been in a continuous loss position for less than 12 months, and those that have been in a continuous loss position for 12 months or more as of December 31, 2019:

	In a Continuous Loss Position for Less than 12 Months					In a Continuous Loss Position for 12 Months or More
	Estimated Fair Value		Unrealized Losses		Total Number of Positions	Estimated Fair Value		Unrealized Losses		Total Number of Positions
	(Dollars in millions)
Corporate debt securities	$	222	$	1	167	$	—	$	—	—
Mortgage-backed securities	143		1		72	—		—		—
Totals	$	365	$	2	239	$	—	$	—	—