Debt (Tables)

12 Months Ended

Dec. 31, 2022

Debt Disclosure [Abstract]

Schedule of debt

Debt at December 31, 2022 and 2021 was as follows:

(In millions)	2022		2021
ATI Inc. 5.875% Senior Notes due 2027	350.0		350.0
ATI Inc. 5.125% Senior Notes due 2031	350.0		350.0
ATI Inc. 4.875% Notes due 2029	325.0		325.0
ATI Inc. 3.5% Convertible Senior Notes due 2025	291.4		291.4
ATI Inc. 4.75% Convertible Senior Notes due 2022	—		84.2
Allegheny Ludlum 6.95% Debentures due 2025 (a)	150.0		150.0
ABL Term Loan	200.0		200.0
U.S. revolving credit facility	—		—
Foreign credit agreements	19.4		27.4
Finance leases and other	79.4		85.7
Debt issuance costs	(17.2)		(20.8)
Total short-term and long-term debt	1,748.0		1,842.9
Short-term debt and current portion of long-term debt	41.7		131.3
Total long-term debt	$	1,706.3	$	1,711.6

(a)The payment obligations of these debentures issued by Allegheny Ludlum, LLC are fully and unconditionally guaranteed by ATI.

Interest Income and Interest Expense Disclosure

Interest expense on the 2025 Convertible Notes was as follows:

	Fiscal year ended December 31,
(in millions)	2022		2021		2020
Contractual coupon rate	$	10.2	$	10.2	$	5.3
Amortization of debt issuance costs	1.8		1.7		0.7
Total interest expense	$	12.0	$	11.9	$	6.0

Interest expense on the 2022 Convertible Notes was as follows:

	Fiscal year ended December 31,
(in millions)	2022		2021		2020
Contractual coupon rate	$	2.0	$	4.0	$	8.6
Amortization of debt issuance costs	0.3		0.5		1.0
Total interest expense	$	2.3	$	4.5	$	9.6