Geographic Information (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from external customers	$ 4,092.2	$ 3,487.7	$ 2,627.3
Inter-company revenue	0	0	0
Total operating revenues	4,092.2	3,487.7	2,627.3
Long-lived assets	312.8	272.4	220.7
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from external customers	2,090.2	1,680.8	1,131.6
Inter-company revenue	(8.1)	9.8	11.0
Total operating revenues	2,082.1	1,690.6	1,142.6
Long-lived assets	196.7	169.3	127.2
United Kingdom/Ireland [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from external customers	1,473.1	1,305.8	1,037.9
Inter-company revenue	(152.8)	(131.3)	(103.7)
Total operating revenues	1,320.3	1,174.5	934.2
Long-lived assets	81.5	79.6	75.0
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from external customers	372.3	370.7	353.1
Inter-company revenue	(14.1)	(10.1)	(8.8)
Total operating revenues	358.2	360.6	344.3
Long-lived assets	7.9	7.6	7.7
Continental Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from external customers	38.8	44.3	42.8
Inter-company revenue	76.7	56.3	43.4
Total operating revenues	115.5	100.6	86.2
Long-lived assets	4.9	2.8	3.1
Asia
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from external customers	117.8	86.1	61.9
Inter-company revenue	98.3	75.3	58.1
Total operating revenues	216.1	161.4	120.0
Long-lived assets	$ 21.8	$ 13.1	$ 7.7