INCOME TAXES - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Deferred Tax Assets and Liabilities
Deferred Tax Assets, debt	$ 176	$ 253
Deferred Tax Assets, property, plant and equipment differences	0	11
Deferred Tax Assets, postretirement benefit accruals	40	27
Deferred Tax Assets, deferred compensation and benefits	55	56
Deferred Tax Assets, asset retirement obligations	155	129
Deferred Tax Assets, net operating loss carryforwards and credits	457	314
Deferred Tax Asset, business interest expense carryforward	194	82
Deferred Tax Assets, investment in partnerships	110	93
Deferred Tax Assets, other	36	17
Deferred Tax Assets, subtotal	1,223	982
Deferred Tax Assets, valuation allowance	(646)	(625)
Deferred Tax Assets, total net deferred taxes	(577)	(357)
Deferred Tax Liabilities, property, plant and equipment differences	(517)	(316)
Deferred Tax Liabilities, all other	(60)	(41)
Deferred Tax Liabilities, total net deferred taxes	(577)	$ (357)
Federal
Deferred Tax Assets and Liabilities
Net operating loss carryforwards	1,000
Tax credit carryforwards	57
State and Local Jurisdiction | CALIFORNIA
Deferred Tax Assets and Liabilities
Net operating loss carryforwards	2,000
Tax credit carryforwards	$ 20