Geographic Information (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from external customers	$ 4,177.0	$ 4,092.2	$ 3,487.7
Inter-company revenue	0	0	0
Total operating revenues	4,177.0	4,092.2	3,487.7
Long-lived assets	349.6	312.8	272.4
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from external customers	2,190.2	2,090.2	1,680.8
Inter-company revenue	(6.5)	(8.1)	9.8
Total operating revenues	2,183.7	2,082.1	1,690.6
Long-lived assets	228.7	196.7	169.3
United Kingdom/Ireland [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from external customers	1,492.1	1,473.1	1,305.8
Inter-company revenue	(144.0)	(152.8)	(131.3)
Total operating revenues	1,348.1	1,320.3	1,174.5
Long-lived assets	83.6	81.5	79.6
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from external customers	346.4	372.3	370.7
Inter-company revenue	(13.2)	(14.1)	(10.1)
Total operating revenues	333.2	358.2	360.6
Long-lived assets	9.4	7.9	7.6
Continental Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from external customers	43.0	38.8	44.3
Inter-company revenue	78.3	76.7	56.3
Total operating revenues	121.3	115.5	100.6
Long-lived assets	7.1	4.9	2.8
Asia
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from external customers	105.3	117.8	86.1
Inter-company revenue	85.4	98.3	75.3
Total operating revenues	190.7	216.1	161.4
Long-lived assets	$ 20.8	$ 21.8	$ 13.1