Retirement Plans (Details) (Operating and Administrative Expenses [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating and Administrative Expenses [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Charges to income for retirement plans	$ 2.5	$ 2.3	$ 2.1