Earnings Per Common Share (EPS) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Basic and diluted:
Income from continuing operations	$ 1,339	$ 1,295	$ 2,595	$ 2,472
Earnings allocated to participating share awards	(14)	(15)	(28)	(30)
Income from discontinued operations, net of tax	0	36	0	36
Net income attributable to common shareholders	1,325	1,316	2,567	2,478
Denominator:
Basic: Weighted-average common stock	1,145	1,190	1,151	1,190
Add: weighted-average stock options	7	7	7	7
Diluted	1,152	1,197	1,158	1,197
Earnings Per Share, Basic [Abstract]
Income from continuing operations attributable to common shareholders	$ 1.16	$ 1.08	$ 2.23	$ 2.05
Income from discontinued operations	$ 0	$ 0.03	$ 0	$ 0.03
Net income attributable to common shareholders	$ 1.16	$ 1.11	$ 2.23	$ 2.08
Earnings Per Share, Diluted [Abstract]
Income from continuing operations attributable to common shareholders	$ 1.15	$ 1.07	$ 2.22	$ 2.04
Income from discontinued operations	$ 0	$ 0.03	$ 0	$ 0.03
Net income attributable to common shareholders	$ 1.15	$ 1.10	$ 2.22	$ 2.07
Earnings Per Common Share Eps Textuals [Abstract]
Subordinated debentures	$ 750	$ 750	$ 750	$ 750
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per Share, amount	8	19	8	20