Marketable securities (Tables)

3 Months Ended

Mar. 31, 2024

Marketable securities

Schedule of Marketable Securities

			Cost or
			amortized		Unrealized
	Market value		cost		loss, net
	(In millions)
December 31, 2023:
Current assets	$	56.1	$	56.1	$	—
Noncurrent assets	$	4.8	$	5.0	$	(.2)
March 31, 2024:
Current assets	$	31.7	$	31.7	$	—
Noncurrent assets	$	5.5	$	5.5	$	—