Stock Compensation Plans (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary of all stock compensation plans
Intrinsic value of awards exercised during the year	$ 3.6	$ 5.1	$ 3.9
Fair value of awards vested during the year	2.9	2.4	3.9
Grant date fair value of awards granted during the year	$ 5.2	$ 4.3	$ 3.4