Investments (Tables)

3 Months Ended

Mar. 31, 2024

Investments, Debt and Equity Securities [Abstract]

Schedule of Investments

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

	March 31, 2024
	Amortized Cost		Gross Unrealized				Estimated Fair Value
			Gains		Losses
	(In millions)
Corporate debt securities	$	2,908	$	8	$	63	$	2,853
Mortgage-backed securities	963		4		44		923
Asset-backed securities	390		1		10		381
Municipal securities	183		—		7		176
U.S. Treasury notes	44		—		—		44
Other	49		—		2		47
Total	$	4,537	$	13	$	126	$	4,424

	December 31, 2023
	Amortized Cost		Gross Unrealized				Estimated Fair Value
			Gains		Losses
	(In millions)
Corporate debt securities	$	2,781	$	16	$	65	$	2,732
Mortgage-backed securities	951		4		44		911
Asset-backed securities	376		1		12		365
Municipal securities	172		—		6		166
U.S. Treasury notes	40		—		—		40
Other	47		—		2		45
Total	$	4,367	$	21	$	129	$	4,259

Schedule of Contractual Maturities of Investments

The contractual maturities of our current investments as of March 31, 2024 are summarized below:

	Amortized Cost		Estimated Fair Value
	(In millions)
Due in one year or less	$	634	$	625
Due after one year through five years	2,419		2,366
Due after five years through ten years	431		427
Due after ten years	1,053		1,006
Total	$	4,537	$	4,424

Schedule of Available-for-Sale Investments

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, 2024:

	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	$	596	$	5	345	$	1,502	$	58	738
Mortgage-backed securities	154		2		137	485		42		267
Asset-backed securities	—		—		—	208		10		97
Municipal securities	—		—		—	112		7		110
Other	—		—		—	16		2		16
Total	$	750	$	7	482	$	2,323	$	119	1,228

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, 2023:

	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	$	263	$	1	160	$	1,553	$	64	754
Mortgage-backed securities	123		2		98	549		42		283
Asset-backed securities	—		—		—	195		12		91
Municipal securities	—		—		—	117		6		116
Other	—		—		—	17		2		17
Total	$	386	$	3	258	$	2,431	$	126	1,261