Employee Benefit Plans - Amounts Recognized in Other Comprehensive Income and Prior Service Cost (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Recognized in Other Comprehensive Income [Abstract]
Net actuarial loss (gain)	$ (11.8)	$ 2.1	$ 13.6
Amortization of net actuarial loss (gain)	(1.2)	(1.1)
Amortization of prior service cost (credit)	0	(0.1)
Total change in other comprehensive income	$ (13.0)	$ 0.9