INCOME TAXES - COMPONENTS OF TAX EXPENSE (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current tax expense (benefit):
Federal	$ (5)	$ 127	$ 392
State	9	35	48
Total current	4	162	440
Deferred tax expense:
Federal	125	(3)	67
State	19	40	12
Total deferred	144	37	79
Income tax expense	$ 148	$ 199	$ 519