Reconciliation of Net Income to Net Income Available to Common Shareholders (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended								6 Months Ended
	Jun. 30, 2019		Mar. 31, 2019		Jun. 30, 2018		Mar. 31, 2018		Jun. 30, 2019	Jun. 30, 2018
Net Income (Loss) Attributable to Parent	$ 688		$ 580		$ 722		$ 643		$ 1,268	$ 1,365
Dividends, Preferred Stock, Cash	(25)	[1]	$ (26)	[1]	(25)	[2]	$ (31)	[2]	(51)	(55)
Net Income (Loss) Available to Common Stockholders, Basic	$ 663				$ 697				$ 1,217	$ 1,310
Weighted Average Number of Shares Outstanding, Basic	443,806				465,529				443,687	467,117
Weighted Average Number of Shares Outstanding, Diluted	446,391				469,339				446,526	471,468
Earnings Per Share, Diluted	$ 1.48				$ 1.49				$ 2.72	$ 2.78
Earnings Per Share, Basic	$ 1.49				$ 1.50				$ 2.74	$ 2.80
Restricted Stock Units (RSUs) [Member]
Dilutive securities	2,100				2,600				2,300	2,700
Warrants, options, and restricted stock [Member]
Dilutive securities	500				1,200				500	1,700

[1] For the three months ended June 30, 2019, dividends were $1,022.22 per share for both Series A and B Preferred Stock, $1,406.25 per share for Series F Preferred Stock, $1,262.50 per share for Series G Preferred Stock, and $1,281.25 per share for Series H Preferred Stock. For the three months ended March 31, 2019, dividends were $1,000.00 per share for both Series A and B Preferred Stock, $1,406.25 per share for Series F Preferred Stock, $1,262.50 per share for Series G Preferred Stock, and $1,281.25 per share for Series H Preferred Stock.

[2] For the three months ended June 30, 2018, dividends were $1,022.22 per share for both Series A and B Preferred Stock, $1,406.25 per share for Series F Preferred Stock, $1,262.50 per share for Series G Preferred Stock, and $1,722.57 per share for Series H Preferred Stock. For the three months ended March 31, 2018, dividends were $1,000.00 per share for both Series A and B Preferred Stock, $1,468.75 per share for Series E Preferred Stock, $1,406.25 per share for Series F Preferred Stock, $1,262.50 per share for Series G Preferred Stock, and $1,281.25 per share for Series H Preferred Stock.