Capital Stock (Details) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Common stock:
Balance, beginning of year	101.0	99.5	98.6
Activity under stock plans	1.4	1.5	0.9
Balance, end of year	102.4	101.0	99.5
Treasury stock:
Balance, beginning of year	2.2	2.2	2.0
Issued under stock plans		(0.5)
Repurchased	0.3	0.5	0.2
Balance, end of year	2.5	2.2	2.2
Common stock outstanding	99.9	98.8	97.3