Our financial instruments measured at fair value on a recurring basis at March 31, 2024, were as follows:


			Observable Inputs		Directly or Indirectly Observable Inputs		Unobservable Inputs
	Total		(Level 1)		(Level 2)		(Level 3)

	(In millions)
Corporate debt securities	$	2,853	$	—	$	2,853	$	—
Mortgage-backed securities	923		—		923		—
Asset-backed securities	381		—		381		—
Municipal securities	176		—		176		—
U.S. Treasury notes	44		—		44		—



Other	47		—		47		—
Total assets	$	4,424	$	—	$	4,424	$	—

Our financial instruments measured at fair value on a recurring basis at December 31, 2023, were as follows:


			Observable Inputs		Directly or Indirectly Observable Inputs		Unobservable Inputs
	Total		(Level 1)		(Level 2)		(Level 3)

	(In millions)
Corporate debt securities	$	2,732	$	—	$	2,732	$	—
Mortgage-backed securities	911		—		911		—
Asset-backed securities	365		—		365		—
Municipal securities	166		—		166		—
U.S. Treasury notes	40		—		40		—


Other	45		—		45		—
Total assets	$	4,259	$	—	$	4,259	$	—