EARNINGS PER COMMON SHARE COMPUTATION (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income available for common stockholders	$ 940	$ 193	$ 1,506	$ 684
Weighted average outstanding shares of common stock used to compute basic earnings per common share (in shares)	135,063	137,763	135,223	137,833
Shares used to compute diluted earnings per common share (in shares)	135,579	138,576	135,770	138,703
Basic earnings per common share (in dollars per share)	$ 6.96	$ 1.40	$ 11.14	$ 4.96
Diluted earnings per common share (in dollars per share)	$ 6.94	$ 1.39	$ 11.10	$ 4.93
Number of antidilutive stock options and restricted stock excluded from computation (in shares)	761	171	732	408
Employee stock options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dilutive effect of employee stock options and restricted stock (in shares)	67	197	98	205
Restricted stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dilutive effect of employee stock options and restricted stock (in shares)	449	616	449	665