Share-based Compensation and Employee Benefits - Schedule of Weighted-Average Actuarial Assumptions (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits
Assumptions related to benefit obligations:
Discount rate	3.17%	4.26%	3.56%
Rate of compensation increase	3.50%	3.50%	3.53%
Assumptions related to benefit costs:
Expected return on plan assets	7.25%	7.25%	7.07%
Rate of compensation increase	3.50%	3.50%	3.52%
OPEB
Defined Benefit Plan Disclosure [Line Items]
UBIT rate	27.00%	21.00%	21.00%
Assumptions related to benefit obligations:
Discount rate	3.03%	4.16%	3.48%
Assumptions related to benefit costs:
Expected return on plan assets	6.50%	7.08%	6.84%
Benefit obligation | Pension Benefits
Assumptions related to benefit costs:
Discount rate	4.26%	3.56%	3.83%
Benefit obligation | OPEB
Assumptions related to benefit costs:
Discount rate	4.16%	3.48%	3.69%
Discount rate for interest on benefit obligations | Pension Benefits
Assumptions related to benefit costs:
Discount rate	3.89%	3.13%	3.09%
Discount rate for interest on benefit obligations | OPEB
Assumptions related to benefit costs:
Discount rate	3.83%	3.08%	3.05%
Discount rate for service cost | Pension Benefits
Assumptions related to benefit costs:
Discount rate	4.28%	3.56%	3.88%
Discount rate for service cost | OPEB
Assumptions related to benefit costs:
Discount rate	4.51%	3.82%	4.15%
Discount rate for interest on service cost | Pension Benefits
Assumptions related to benefit costs:
Discount rate	3.93%	3.14%	3.24%
Discount rate for interest on service cost | OPEB
Assumptions related to benefit costs:
Discount rate	4.46%	3.76%	3.95%