Per Share Information (Tables)

3 Months Ended

Mar. 31, 2021

Earnings Per Share [Abstract]

Schedule Of Earnings Per Share Diluted By Common Class

The following table sets forth the computation of basic and diluted income (loss) per common share: 

	Three months ended
(In millions, except per share amounts)	March 31,
	2021		2020
Numerator:
Numerator for basic income (loss) per common share –
Net income (loss) attributable to ATI	$	(7.9)	$	21.1
Effect of dilutive securities:
4.75% Convertible Senior Notes due 2022	—		2.3
3.5% Convertible Senior Notes due 2025	—		—
Numerator for diluted income (loss) per common share –
Net income (loss) attributable to ATI after assumed conversions	$	(7.9)	$	23.4
Denominator:
Denominator for basic net income (loss) per common share – weighted average shares	126.8		126.1
Effect of dilutive securities:
Share-based compensation	—		0.4
4.75% Convertible Senior Notes due 2022	—		19.9
3.5% Convertible Senior Notes due 2025	—		—
Denominator for diluted net income (loss) per common share – adjusted weighted average shares and assumed conversions	126.8		146.4
Basic net income (loss) attributable to ATI per common share	$	(0.06)	$	0.17
Diluted net income (loss) attributable to ATI per common share	$	(0.06)	$	0.16