ACCUMULATED OTHER COMPREHENSIVE INCOME - Summary of Changes in AOCI by Component (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Gains (losses)
Beginning of period	$ 8,535	$ 8,160	$ 8,726	$ 7,912
Other comprehensive income (loss) before reclassifications			(239)	(162)
Amounts reclassified from AOCI			71	33
Total other comprehensive income (loss), net of tax	(106)	149	(168)	(129)
End of period	8,815	8,602	8,815	8,602
CTA
Gains (losses)
Beginning of period			(2,587)	(2,954)
Other comprehensive income (loss) before reclassifications			(257)	(43)
Amounts reclassified from AOCI			0	0
Total other comprehensive income (loss), net of tax			(257)	(43)
End of period	(2,844)	(2,997)	(2,844)	(2,997)
Pension and OPEB plans
Gains (losses)
Beginning of period			(574)	(715)
Other comprehensive income (loss) before reclassifications			13	(9)
Amounts reclassified from AOCI			50	35
Total other comprehensive income (loss), net of tax			63	26
End of period	(511)	(689)	(511)	(689)
Hedging activities
Gains (losses)
Beginning of period			(153)	(41)
Other comprehensive income (loss) before reclassifications			5	(110)
Amounts reclassified from AOCI			21	(2)
Total other comprehensive income (loss), net of tax			26	(112)
End of period	(127)	(153)	(127)	(153)
Accumulated Other Comprehensive Income (Loss)
Gains (losses)
Beginning of period			(3,314)	(3,710)
End of period	$ (3,482)	$ (3,839)	$ (3,482)	$ (3,839)