Acquisition (Details 2) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Acquisition
Total revenues - Pro forma	$ 2,210.6	$ 2,157.7	$ 4,427.3	$ 4,316.8
Net income (loss) - Pro forma	$ 236.6	$ 205.5	$ 447.1	$ 455.7
Basic earnings (loss) per common share (in dollars per share) - Pro forma	$ 0.76	$ 0.69	$ 1.52	$ 1.52
Diluted earnings (loss) per common share (in dollars per share) - Pro forma	$ 0.75	$ 0.68	$ 1.51	$ 1.50