Pension and Other Postretirement Benefits (Details 8) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined contribution retirement plans
Pension and other postretirement benefits
Cost recognized	$ 1.8	$ 1.6	$ 1.5
Supplemental retirement contribution plan
Pension and other postretirement benefits
Cost recognized	0.2	0.1
Supplemental retirement contribution plan | Maximum
Pension and other postretirement benefits
Cost recognized			0.1
Voluntary contribution investment plans
Pension and other postretirement benefits
Cost recognized	$ 1.7	$ 1.5	$ 1.3