SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Future Expected Operating Lease Payments and Expected Obligations for Power Purchase and Other Lease Commitments) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Future Expected Operating Lease Payments
2019	$ 450
2020	679
2021	623
2022	548
2023	255
Thereafter	692
Total lease payments	3,247
Less imputed interest	(594)
Total	$ 2,653
Future Expected Obligations and Other Lease Commitments
2019		$ 684
2020		677
2021		621
2022		546
2023		252
Thereafter		581
Total lease commitments		$ 3,361

Amount of lessee's undiscounted obligation for lease payments for operating lease.

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Amount of lessee's undiscounted obligation for lease payments for operating lease having an initial or remaining lease term in excess of one year due in remainder of fiscal year following latest fiscal year.

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