INCOME TAXES - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Deferred Tax Assets and Liabilities
Deferred Tax Assets, debt	$ 693.0	$ 608.0
Deferred Tax Assets, property, plant and equipment differences	60.0	132.0
Deferred Tax Assets, postretirement benefit accruals	45.0	41.0
Deferred Tax Assets, deferred compensation and benefits	74.0	75.0
Deferred Tax Assets, asset retirement obligations	183.0	156.0
Deferred Tax Assets, federal effect of state income taxes		28.0
Deferred Tax Assets, net operating loss carryforwards	61.0	7.0
Deferred Tax Assets, all other	39.0	47.0
Deferred Tax Assets, subtotal	1,155.0	1,094.0
Deferred Tax Assets, valuation allowance	(780.0)	(382.0)
Deferred Tax Assets, total net deferred taxes	375.0	712.0
Deferred Tax Liabilities, property, plant and equipment differences	(335.0)	(427.0)
Deferred Tax Liabilities, federal effect of state income taxes		(24.0)
Deferred Tax Liabilities, all other	(40.0)	(3.0)
Deferred Tax Liabilities	(375.0)	(454.0)
Gross deferred tax assets realizable	375.0
Amounts due to Occidental under tax sharing agreement	$ 0.0	$ 0.0
Minimum tax position realized upon settlement (as a percent)	50.00%
Deferred tax liability on prior period tax positions	$ 25.0
CALIFORNIA | State and Local Jurisdiction
Deferred Tax Assets and Liabilities
Net operating loss carryforwards	777.0
Unrecognized tax benefits on net operating loss carryforward	$ 88.0