Derivative Instruments and Hedging Activities - Fair Value of Derivative Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2021	Sep. 30, 2021	Dec. 31, 2020
Derivative assets:
Total derivative assets — gross	$ 1,156	$ 1,687	$ 185
Gross amounts offset in the balance sheet	(116)	(216)	(48)
Cash collateral received	(205)	(468)	(6)
Total derivative assets — net	835	1,003	131
Derivative liabilities:
Total derivative liabilities — gross	(202)	(317)	(147)
Gross amounts offset in the balance sheet	116	216	48
Cash collateral pledged	0	3	0
Total derivative liabilities — net	(86)	(98)	(99)
Commodity contracts
Derivative assets:
Total derivative assets — gross	10	58	1
Derivative liabilities:
Total derivative liabilities — gross	(7)	(23)	(2)
Derivatives designated as hedging instruments:
Derivative assets:
Total derivative assets — gross	15	20	8
Derivative liabilities:
Total derivative liabilities — gross	(20)	(29)	(50)
Derivatives designated as hedging instruments: | Foreign currency contracts
Derivative assets:
Total derivative assets — gross	10	20	8
Derivative liabilities:
Total derivative liabilities — gross	(3)	0	0
Derivatives designated as hedging instruments: | Interest rate contracts
Derivative assets:
Total derivative assets — gross	5	0	0
Derivative liabilities:
Total derivative liabilities — gross	(17)	(29)	(50)
Derivatives not designated as hedging instruments:
Derivative assets:
Total derivative assets — gross	1,131	1,609	176
Derivative liabilities:
Total derivative liabilities — gross	(175)	(265)	(95)
Derivatives not designated as hedging instruments: | Foreign currency contracts
Derivative assets:
Total derivative assets — gross	19	18	6
Derivative liabilities:
Total derivative liabilities — gross	(4)	(8)	(25)
Derivatives not designated as hedging instruments: | Commodity contracts
Derivative assets:
Total derivative assets — gross	1,112	1,591	170
Derivative liabilities:
Total derivative liabilities — gross	$ (171)	$ (257)	$ (70)