INCOME TAXES - COMPONENTS OF TAX EXPENSE (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current tax expense (benefit):
Federal	$ 397	$ 229	$ 145
State	30	27	17
Total current	427	256	162
Deferred tax expense:
Federal	60	103	131
State	(23)	11	15
Total deferred	37	114	146
Total tax expense related to income	$ 464	$ 370	$ 308