EARNINGS PER COMMON SHARE COMPUTATION - Schedule of Details Supporting Computation of Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income available for common stockholders	$ 355	$ 644	$ 193	$ 491	$ 184	$ 499	$ 650	$ 1,115	$ 1,683	$ 2,448	$ 614
Weighted-average outstanding shares of common stock used to compute basic earnings per common share (in shares)									137,486	144,493	149,375
Shares used to compute diluted earnings per common share (in shares)									138,403	145,585	150,917
Basic earnings per common share (in USD per share)	$ 2.60	$ 4.68	$ 1.40	$ 3.56	$ 1.30	$ 3.46	$ 4.49	$ 7.54	$ 12.24	$ 16.94	$ 4.11
Diluted earnings per common share (in USD per share)	$ 2.58	$ 4.65	$ 1.39	$ 3.53	$ 1.29	$ 3.44	$ 4.46	$ 7.49	$ 12.16	$ 16.81	$ 4.07
Number of antidilutive stock options and restricted stock awards excluded from computation (in shares)									223	539	748
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)									194	172	219
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)									723	920	1,323