Earnings Per Common Share (EPS) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Basic and diluted:
Net income	$ 1,477	$ 1,366	$ 4,438	$ 4,051
Earnings allocated to participating share awards	(11)	(12)	(35)	(36)
Net income attributable to common shareholders	1,466	1,354	4,403	4,015
Denominator:
Basic	1,041,000,000	1,074,000,000	1,051,000,000	1,087,000,000
Add: Weighted-average stock options	6,000,000	7,000,000	6,000,000	7,000,000
Diluted	1,047,000,000	1,081,000,000	1,057,000,000	1,094,000,000
Earnings Per Common Share, Basic [Abstract]
Income from continuing operations attributable to common shareholders	$ 1.41	$ 1.26	$ 4.19	$ 3.69
Earnings Per Common Share, Diluted [Abstract]
Income from continuing operations attributable to common shareholders	$ 1.4	$ 1.25	$ 4.17	$ 3.67
Earnings Per Common Share (Textuals) [Abstract]
Subordinated debentures	$ 750	$ 750	$ 750	$ 750
Subordinated debt issuance year	2006	2006	2006	2006
Subordinated debt maturity year	2036	2036	2036	2036
Stock options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per Share, amount	200,000	100,000	200,000	200,000