INCOME TAXES - Reconciliation of Income Tax Expense with Federal Income Taxes at the Statutory Rate (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of income tax expense with federal income taxes at the statutory rate
Federal income tax	$ 254	$ 227	$ 327
State income taxes, net of federal income tax benefit	36	32	20
Clean energy credit	0	(20)	(38)
Foreign rate difference	25	20	10
Goodwill impairment	0	20	0
U.S. tax legislation impact	0	0	(3)
Excess tax benefits from stock-based compensation	(2)	(15)	(14)
Other - net	1	(6)	11
Income tax expense	$ 314	$ 258	$ 313
Effective tax rate	26.00%	23.90%	33.50%