Employee Benefit Plans - Pension Obligation and Funded Status (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Pension Plan [Member]
Change in benefit obligations [Rollforward]
Beginning projected benefit obligation	$ 63.8	$ 58.1
Service cost	1.7	1.7	1.5
Interest cost	2.6	2.7	2.6
Actuarial (gain)/loss	(6.8)	2.6
Benefits paid	(1.4)	(1.3)
Ending projected benefit obligation	59.9	63.8	58.1
Change in plan assets [Rollforward]
Beginning fair value	39.1	34.5
Actual return	6.2	4.3
Company contribution	1.2	1.7
Benefits paid	(1.4)	(1.4)
Ending fair value	45.1	39.1	34.5
Funded status of the plan	(14.8)	(24.7)
Supplementary Pension Plan [Member]
Change in benefit obligations [Rollforward]
Beginning projected benefit obligation	13.2	11.6
Service cost	0.4	0.3	0.2
Interest cost	0.5	0.5	0.5
Actuarial (gain)/loss	(1.6)	1.2
Benefits paid	(0.4)	(0.4)
Ending projected benefit obligation	12.1	13.2	11.6
Change in plan assets [Rollforward]
Beginning fair value	0	0
Company contribution	0.4	0.4
Benefits paid	(0.4)	(0.4)
Ending fair value	0	0	0
Funded status of the plan	$ (12.1)	$ (13.2)