Segment and Geographic Information (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment and Geographic Information
Revenues	$ 658.6	$ 632.0	$ 632.8	$ 653.2	$ 623.4	$ 591.4	$ 582.2	$ 591.7	$ 2,576.6	$ 2,388.7	$ 2,328.5
Foreign revenues									471.5	434.7	267.5
Long-lived assets	538.3				562.1				538.3	562.1
Foreign long-lived assets	123.4				127.4				123.4	127.4
U.S.
Segment and Geographic Information
Revenues									2,105.1	1,954.0	2,061.0
Long-lived assets	414.9				434.7				414.9	434.7
U.K.
Segment and Geographic Information
Foreign revenues									279.6	242.9	133.8
Foreign long-lived assets	82.7				91.8				82.7	91.8
Canada
Segment and Geographic Information
Foreign revenues									65.1	60.7	49.7
Foreign long-lived assets	29.9				23.2				29.9	23.2
Australia
Segment and Geographic Information
Foreign revenues									74.2	66.3	45.7
Foreign long-lived assets	6.3				7.4				6.3	7.4
Others
Segment and Geographic Information
Foreign revenues									52.6	64.8	38.3
Foreign long-lived assets	$ 4.5				$ 5.0				$ 4.5	$ 5.0