PREFERRED STOCK (Details)		3 Months Ended	9 Months Ended	12 Months Ended
	Apr. 18, 2016 USD ($)	Mar. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) $ / shares shares
Preferred stock
Carrying value		$ 17,753,000,000		$ 16,718,000,000
Distribution of preferred dividends		$ 210,000,000
Forecast
Preferred stock
Distribution of preferred dividends			$ 868,000,000
Series AA
Preferred stock
Dividend rate (as a percent)		8.125%		8.125%
Redemption price per depositary share/ preference share (in dollars per share) | $ / shares		$ 25		$ 25
Number of depositary shares (in shares) | shares		3,870,330		3,870,330
Carrying value		$ 97,000,000		$ 97,000,000
Depositary shares, interest in corresponding series of preferred stock		0.001
Series E
Preferred stock
Dividend rate (as a percent)		8.40%		8.40%
Redemption price per depositary share/ preference share (in dollars per share) | $ / shares		$ 1,000		$ 1,000
Number of depositary shares (in shares) | shares		121,254		121,254
Carrying value		$ 121,000,000		$ 121,000,000
Depositary shares, interest in corresponding series of preferred stock		0.04
Series A
Preferred stock
Dividend rate (as a percent)		5.95%		5.95%
Redemption price per depositary share/ preference share (in dollars per share) | $ / shares		$ 1,000		$ 1,000
Number of depositary shares (in shares) | shares		1,500,000		1,500,000
Carrying value		$ 1,500,000,000		$ 1,500,000,000
Depositary shares, interest in corresponding series of preferred stock		0.04
Series B
Preferred stock
Dividend rate (as a percent)		5.90%		5.90%
Redemption price per depositary share/ preference share (in dollars per share) | $ / shares		$ 1,000		$ 1,000
Number of depositary shares (in shares) | shares		750,000		750,000
Carrying value		$ 750,000,000		$ 750,000,000
Depositary shares, interest in corresponding series of preferred stock		0.04
Series C
Preferred stock
Dividend rate (as a percent)		5.80%		5.80%
Redemption price per depositary share/ preference share (in dollars per share) | $ / shares		$ 25		$ 25
Number of depositary shares (in shares) | shares		23,000,000		23,000,000
Carrying value		$ 575,000,000		$ 575,000,000
Depositary shares, interest in corresponding series of preferred stock		0.001
Series D
Preferred stock
Dividend rate (as a percent)		5.35%		5.35%
Redemption price per depositary share/ preference share (in dollars per share) | $ / shares		$ 1,000		$ 1,000
Number of depositary shares (in shares) | shares		1,250,000		1,250,000
Carrying value		$ 1,250,000,000		$ 1,250,000,000
Depositary shares, interest in corresponding series of preferred stock		0.04
Series J
Preferred stock
Dividend rate (as a percent)		7.125%		7.125%
Redemption price per depositary share/ preference share (in dollars per share) | $ / shares		$ 25		$ 25
Number of depositary shares (in shares) | shares		38,000,000		38,000,000
Carrying value		$ 950,000,000		$ 950,000,000
Depositary shares, interest in corresponding series of preferred stock		0.001
Series K
Preferred stock
Dividend rate (as a percent)		6.875%		6.875%
Redemption price per depositary share/ preference share (in dollars per share) | $ / shares		$ 25		$ 25
Number of depositary shares (in shares) | shares		59,800,000		59,800,000
Carrying value		$ 1,495,000,000		$ 1,495,000,000
Depositary shares, interest in corresponding series of preferred stock		0.001
Series L
Preferred stock
Dividend rate (as a percent)		6.875%		6.875%
Redemption price per depositary share/ preference share (in dollars per share) | $ / shares		$ 25		$ 25
Number of depositary shares (in shares) | shares		19,200,000		19,200,000
Carrying value		$ 480,000,000		$ 480,000,000
Depositary shares, interest in corresponding series of preferred stock		0.001
Series M
Preferred stock
Dividend rate (as a percent)		6.30%		6.30%
Redemption price per depositary share/ preference share (in dollars per share) | $ / shares		$ 1,000		$ 1,000
Number of depositary shares (in shares) | shares		1,750,000		1,750,000
Carrying value		$ 1,750,000,000		$ 1,750,000,000
Depositary shares, interest in corresponding series of preferred stock		0.04
Series N
Preferred stock
Dividend rate (as a percent)		5.80%		5.80%
Redemption price per depositary share/ preference share (in dollars per share) | $ / shares		$ 1,000		$ 1,000
Number of depositary shares (in shares) | shares		1,500,000		1,500,000
Carrying value		$ 1,500,000,000		$ 1,500,000,000
Depositary shares, interest in corresponding series of preferred stock		0.04
Series O
Preferred stock
Dividend rate (as a percent)		5.875%		5.875%
Redemption price per depositary share/ preference share (in dollars per share) | $ / shares		$ 1,000		$ 1,000
Number of depositary shares (in shares) | shares		1,500,000		1,500,000
Carrying value		$ 1,500,000,000		$ 1,500,000,000
Depositary shares, interest in corresponding series of preferred stock		0.04
Series P
Preferred stock
Dividend rate (as a percent)		5.95%		5.95%
Redemption price per depositary share/ preference share (in dollars per share) | $ / shares		$ 1,000		$ 1,000
Number of depositary shares (in shares) | shares		2,000,000		2,000,000
Carrying value		$ 2,000,000,000		$ 2,000,000,000
Depositary shares, interest in corresponding series of preferred stock		0.04
Series Q
Preferred stock
Dividend rate (as a percent)		5.95%		5.95%
Redemption price per depositary share/ preference share (in dollars per share) | $ / shares		$ 1,000		$ 1,000
Number of depositary shares (in shares) | shares		1,250,000		1,250,000
Carrying value		$ 1,250,000,000		$ 1,250,000,000
Depositary shares, interest in corresponding series of preferred stock		0.04
Series R
Preferred stock
Dividend rate (as a percent)		6.125%		6.125%
Redemption price per depositary share/ preference share (in dollars per share) | $ / shares		$ 1,000		$ 1,000
Number of depositary shares (in shares) | shares		1,500,000		1,500,000
Carrying value		$ 1,500,000,000		$ 1,500,000,000
Depositary shares, interest in corresponding series of preferred stock		0.04
Series S
Preferred stock
Dividend rate (as a percent)		6.30%
Redemption price per depositary share/ preference share (in dollars per share) | $ / shares		$ 25
Number of depositary shares (in shares) | shares		41,400,000
Carrying value		$ 1,035,000,000		$ 0
Depositary shares, interest in corresponding series of preferred stock		0.001
Series T | Subsequent event
Preferred stock
Dividend rate (as a percent)	6.25%
Carrying value	$ 1,500,000,000.0
Depositary shares, interest in corresponding series of preferred stock	0.04
Series T | Subsequent event | Three-Month LIBOR
Preferred stock
Dividend rate, basis spread on variable rate (as percent)	4.517%