Common Equity (Tables)

12 Months Ended

Dec. 31, 2019

Equity [Abstract]

Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]

The following table calculates basic and diluted earnings per share for the Company.

(In millions except per share data)	2019		2018		2017
Net income	$	433.6	$	425.5	$	619.0
Average common shares outstanding:
Basic average common shares outstanding	200.1		199.7		199.7
Effect of dilutive securities:
Contingently issuable shares (performance and restricted stock units)	0.6		0.8		0.3
Diluted average common shares outstanding	200.7		200.5		200.0
Basic earnings per average common share	$	2.17	$	2.13	$	3.10
Diluted earnings per average common share	$	2.16	$	2.12	$	3.10
Anti-dilutive shares excluded from earnings per share calculation	—		—		—