STOCKHOLDERS' EQUITY (Details) - USD ($) $ / shares in Units, $ in Millions			9 Months Ended		12 Months Ended
	Oct. 25, 2018	May 24, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Preferred Stock
Preferred stock, authorized (in shares)			100,000,000		100,000,000
Preferred stock, outstanding (in shares)			550,000		250,000
Preferred stock, par value (in dollars per share)			$ 25		$ 25.00
Preferred stock, shares issued (in shares)			550,000		250,000
Preferred stock, carrying amount			$ 543		$ 247
Preferred stock issued			296
Treasury Stock
Treasury stock purchased			$ 725	$ 485
Treasury stock purchased (in shares)			17,527,586
Series B Preferred Stock
Preferred Stock
Preferred stock, par value (in dollars per share)		$ 25
Preferred stock issued		$ 300
Preferred stock issued (in shares)		300,000
Preferred stock, dividend rate		6.00%
Preferred stock, liquidation preference per share (in dollars per share)		$ 1,000
Preferred stock, redemption notice period		90 days
Preferred stock, redemption price per share (in dollars per share)		$ 1,000
Carrying amount of preferred stock		$ 296
Series A Preferred Stock
Preferred Stock
Preferred stock, shares issued (in shares)			250,000		250,000
Preferred stock, dividend rate			5.50%		5.50%
Preferred stock, liquidation preference per share (in dollars per share)			$ 1,000		$ 1,000
Carrying amount of preferred stock			$ 247		$ 247
LIBOR | Series B Preferred Stock
Preferred Stock
Preferred stock, dividend payment rate, basis spread on variable rate		3.003%
Subsequent Event [Member] | Series C Preferred Stock
Preferred Stock
Preferred stock, par value (in dollars per share)	$ 25
Preferred stock issued	$ 300
Preferred stock issued (in shares)	300,000
Preferred stock, dividend rate	6.375%
Preferred stock, liquidation preference per share (in dollars per share)	$ 1,000
Preferred stock, redemption notice period	90 days
Preferred stock, redemption price per share (in dollars per share)	$ 1,000
Carrying amount of preferred stock	$ 296
Subsequent Event [Member] | LIBOR | Series C Preferred Stock
Preferred Stock
Preferred stock, dividend payment rate, basis spread on variable rate	3.157%