Derivative Instruments - Cumulative Fair Value Hedging Adjustments (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Commodity contracts
Assets
Carrying amount of the hedged items	$ 6,700	$ 6,800
Long-term debt
Liabilities
Carrying amount of the hedged items	145,917	139,915
Cumulative amount of fair value hedging adjustments included in the carrying amount of hedged items:
Active hedging relationships	2,589	141
Discontinued hedging relationships	22	8
Total	2,611	149
Long-term debt | Not designated as hedges
Liabilities
Carrying amount of the hedged items	7,100	7,300
Beneficial interests issued by consolidated VIEs
Liabilities
Carrying amount of the hedged items	6,997	6,987
Cumulative amount of fair value hedging adjustments included in the carrying amount of hedged items:
Active hedging relationships	0	0
Discontinued hedging relationships	(24)	(33)
Total	(24)	(33)
Investment securities - AFS
Assets
Carrying amount of the hedged items	62,705	55,313
Cumulative amount of fair value hedging adjustments included in the carrying amount of hedged items:
Active hedging relationships	(112)	(1,105)
Discontinued hedging relationships	320	381
Total	208	(724)
Investment securities - AFS | Not designated as hedges
Assets
Carrying amount of the hedged items	$ 13,200	$ 14,600