Acquisition (Details 2) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Acquisition
Total revenues - Pro forma	$ 2,239.6	$ 2,756.8	$ 6,666.9	$ 7,073.6
Net income (loss) - Pro forma	$ 259.1	$ 224.1	$ 706.4	$ 679.8
Basic earnings (loss) per common share (in dollars per share) - Pro forma	$ 0.83	$ 0.76	$ 2.40	$ 2.28
Diluted earnings (loss) per common share (in dollars per share) - Pro forma	$ 0.82	$ 0.75	$ 2.37	$ 2.26