Capital Stock (Details) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Common stock:
Balance, beginning of year	99.5	98.6	98.3
Activity under stock plans	1.5	0.9	0.3
Balance, end of year	101.0	99.5	98.6
Treasury stock:
Balance, beginning of year	2.2	2.0	1.9
Issued under stock plans	(0.5)
Repurchased	0.5	0.2	0.1
Balance, end of year	2.2	2.2	2.0
Common stock outstanding	98.8	97.3	96.6