Debt (Tables)

9 Months Ended

Sep. 30, 2022

Debt Disclosure [Abstract]

Schedule of Debt Instruments

Debt at September 30, 2022 and December 31, 2021 was as follows (in millions): 

	September 30, 2022		December 31, 2021
ATI Inc. 5.875% Notes due 2027	350.0		350.0
ATI Inc. 5.125% 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
Term Loan due 2027	200.0		200.0
U.S. revolving credit facility	—		—
Foreign credit facilities	8.5		27.4
Finance leases and other	72.4		85.7
Debt issuance costs	(18.0)		(20.8)
Debt	1,729.3		1,842.9
Short-term debt and current portion of long-term debt	28.9		131.3
Long-term debt	$	1,700.4	$	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:

	Three months ended September 30,				Nine months ended September 30,
(in millions)	2022		2021		2022		2021
Contractual coupon rate	$	2.5	$	2.5	$	7.6	$	7.6
Amortization of debt issuance costs	0.4		0.5		1.3		1.3
Total interest expense	$	2.9	$	3.0	$	8.9	$	8.9

Interest expense on the 2022 Convertible Notes was as follows:

	Three months ended September 30,				Nine months ended September 30,
(in millions)	2022		2021		2022		2021
Contractual coupon rate	$	—	$	1.0	$	2.0	$	3.0
Amortization of debt issuance costs	—		0.2		0.3		0.4
Total interest expense	$	—	$	1.2	$	2.3	$	3.4