Earnings (Loss) Per Share (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net income	$ 727.5	$ 1,203.1	$ 1,206.2	$ 1,548.0	$ 827.2	$ 1,326.6	$ 923.6	$ 1,011.1	$ 4,684.8	$ 4,088.6	$ 4,347.7
Weighted Average Number of Shares Outstanding, Basic									1,080,874	1,113,178	1,113,923
Earnings per share - basic	$ 0.68	$ 1.11	$ 1.12	$ 1.42	$ 0.75	$ 1.18	$ 0.83	$ 0.91	$ 4.33	$ 3.67	$ 3.90
Weighted Average Number of Shares Outstanding, Diluted									1,084,766	1,117,294	1,113,967
Earnings per share - diluted	$ 0.67	$ 1.11	$ 1.11	$ 1.42	$ 0.74	$ 1.18	$ 0.83	$ 0.91	$ 4.32	$ 3.66	$ 3.90