Share-based Compensation and Employee Benefits - Schedule of Components of Net Benefit Cost and Other Amounts Recognized in Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits
Components of net benefit cost (credit):
Service cost	$ 53	$ 52	$ 40
Interest cost	96	84	88
Expected return on assets	(129)	(149)	(147)
Amortization of prior service cost (credit)	0	0	1
Amortization of net actuarial loss (gain)	54	40	52
Curtailment and settlement loss	0	0	5
Net benefit cost (credit)	74	27	39
Other changes in plan assets and benefit obligations recognized in other comprehensive (income) loss:
Net (gain) loss arising during period	(42)	105	17
Amortization or settlement recognition of net actuarial (loss) gain	(54)	(87)	(64)
Amortization of prior service (cost) credit	0	(1)	(1)
Total recognized in total other comprehensive (income) loss	(96)	17	(48)
Total recognized in net benefit cost (credit) and other comprehensive (income) loss	(22)	44	(9)
OPEB
Components of net benefit cost (credit):
Service cost	1	1	1
Interest cost	12	12	13
Expected return on assets	(16)	(20)	(19)
Amortization of prior service cost (credit)	(4)	(4)	(3)
Amortization of net actuarial loss (gain)	(11)	(6)	(6)
Curtailment and settlement loss	0	0	0
Net benefit cost (credit)	(18)	(17)	(14)
Other changes in plan assets and benefit obligations recognized in other comprehensive (income) loss:
Net (gain) loss arising during period	(17)	(32)	(25)
Amortization or settlement recognition of net actuarial (loss) gain	11	3	6
Amortization of prior service (cost) credit	2	3	1
Total recognized in total other comprehensive (income) loss	(4)	(26)	(18)
Total recognized in net benefit cost (credit) and other comprehensive (income) loss	$ (22)	$ (43)	$ (32)