Capital Stock (Tables)

12 Months Ended

Dec. 31, 2020

Equity [Abstract]

Schedule of Weighted Average Number of Shares

Shares Used to Calculate Earnings per Share

	Years Ended December 31,
(In millions)	2020	2019	2018
Weighted-average shares
Basic(a)	50.4	50.2	50.9
Effect of dilutive stock awards	0.4	0.9	—
Diluted(a)	50.8	51.1	50.9
Antidilutive stock awards excluded from denominator	0.6	0.1	1.6

(a)We have deferred compensation plans for directors and certain of our employees.  Some amounts owed to participants are denominated in common stock units.  Each unit represents one share of common stock.  The number of shares used to calculate basic earnings per share includes the weighted-average common stock units credited to employees and directors under the deferred compensation plans.  Additionally, nonvested units containing only a service requirement are also included in the computation of basic weighted-average shares when the requisite service period has been completed.  Accordingly, basic and diluted shares include weighted-average units of 0.3 million in 2020, 0.3 million in 2019 and 0.3 million in 2018.