Capital Stock (Tables)

12 Months Ended

Dec. 31, 2020

Stockholders Equity Note [Abstract]

Schedule of Common Stock Outstanding

Common stock outstanding as of December 31, 2020, 2019 and 2018 was as follows:

(Number of shares in millions)	2020		2019		2018
Common stock:
Balance, beginning of year	109.3		108.5		107.8
Activity under stock plans		0.4		0.8		0.7
Balance, end of year	109.7		109.3		108.5
Treasury stock:
Balance, beginning of year	25.7		23.7		18.2
Repurchased		0.4		2.0		5.5
Balance, end of year	26.1		25.7		23.7
Common stock outstanding	83.6		83.6		84.8