Earnings Per Common Share (EPS) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Basic and diluted:
Net income		$ 1,426	$ 1,525
Preferred dividends		(21)	0
Net income available to common stockholders - basic		1,405	1,525
Net income available to common stockholders - diluted		1,405	1,525
Earnings allocated to participating share awards		(11)	(11)
Net income attributable to common shareholders		$ 1,394	$ 1,514
Denominator:
Basic		961,000,000	1,019,000,000
Add: Weighted-average stock options		2,000,000	4,000,000
Diluted		963,000,000	1,023,000,000
Earnings Per Common Share, Basic (Note 15) [Abstract]
Income from continuing operations attributable to common shareholders	[1]	$ 1.45	$ 1.49
Earnings Per Common Share, Diluted (Note 15) [Abstract]
Income from continuing operations attributable to common shareholders	[1]	$ 1.45	$ 1.48
Earnings Per Common Share (Textuals) [Abstract]
Subordinated debentures		$ 750	$ 750
Subordinated debt issuance year		2006	2006
Subordinated debt maturity year		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		1,500,000	500,000

[1] Represents net income less ( i ) earnings allocated to participating share awards of $11 million for both the three months ended March 31 , 2016 and 2015 , and (ii) dividends on preferred shares of $ 21 million and nil for the three months ended March 31 , 2016 and 2015 , respectively.