Capital Stock - Schedule of Common Stock Outstanding (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Common stock:
Balance, beginning of year	108.5	107.8	106.7
Activity under stock plans	0.8	0.7	1.1
Balance, end of year	109.3	108.5	107.8
Treasury stock:
Balance, beginning of year	23.7	18.2	15.3
Repurchased	2.0	5.5	2.9
Balance, end of year	25.7	23.7	18.2
Common stock outstanding	83.6	84.8	89.6