COMMITMENTS AND CONTINGENCIES COMMITMENTS AND CONTINGENCIES - Summary of Estimated Synthetic Lease Covenant Calculations (Details)	Dec. 31, 2017 USD ($)
Minimum
Debt Instrument [Line Items]
Consolidated net worth margin, requirement	$ 0.00
Consolidated net worth margin, actual results	4,000,000,000
Total adjusted capital margin, requirement	0.0
Total adjusted capital margin, actual results	$ 3,000,000,000
Interest cash inflow available compared to adjusted consolidated interest expense, requirement	2.0
Interest cash inflow available compared to adjusted consolidated interest expense, actual results	9.0
Maximum
Debt Instrument [Line Items]
Debt to total capital ratio, requirement	40.00%
Debt to total capital ratio, actual results	19.00%