Capital Stock (Tables)

12 Months Ended

Dec. 31, 2016

Stockholders Equity Note [Abstract]

Schedule of Common Stock Outstanding

Common stock outstanding as of December 31, 2016, 2015 and 2014 was as follows:

(Number of shares in millions)	2016		2015		2014
Common stock:
Balance, beginning of year		106.0		104.8		104.0
Activity under stock plans		0.7		1.2		0.8
Balance, end of year		106.7		106.0		104.8
Treasury stock:
Balance, beginning of year		12.5		9.3		5.1
Repurchased		2.8		3.2		4.2
Balance, end of year		15.3		12.5		9.3
Common stock outstanding		91.4		93.5		95.5