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Share-based Compensation and Employee Benefits (Schedule of Weighted-Average Actuarial Assumptions) (Details)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Pension Benefits [Member]      
Assumptions related to benefit obligations:      
Discount rate 4.26% 3.56% 3.83%
Rate of compensation increase 3.50% 3.53% 3.52%
Assumptions related to benefit costs:      
Expected return on plan assets 7.25% 7.07% 7.31%
Rate of compensation increase 3.50% 3.52% 3.51%
OPEB [Member]      
Defined Benefit Plan Disclosure [Line Items]      
UBIT rate 21.00% 21.00% 21.00%
Assumptions related to benefit obligations:      
Discount rate 4.16% 3.48% 3.69%
Assumptions related to benefit costs:      
Expected return on plan assets 7.08% 6.84% 7.07%
Benefit obligation [Member] | Pension Benefits [Member]      
Assumptions related to benefit costs:      
Discount rate 3.56% 3.83% 4.05%
Benefit obligation [Member] | OPEB [Member]      
Assumptions related to benefit costs:      
Discount rate 3.48% 3.69% 3.91%
Discount rate for interest on benefit obligations [Member] | Pension Benefits [Member]      
Assumptions related to benefit costs:      
Discount rate 3.13% 3.09% 3.24%
Discount rate for interest on benefit obligations [Member] | OPEB [Member]      
Assumptions related to benefit costs:      
Discount rate 3.08% 3.05% 3.18%
Discount rate for service cost [Member] | Pension Benefits [Member]      
Assumptions related to benefit costs:      
Discount rate 3.56% 3.88% 4.15%
Discount rate for service cost [Member] | OPEB [Member]      
Assumptions related to benefit costs:      
Discount rate 3.82% 4.15% 4.36%
Discount rate for interest on service cost [Member] | Pension Benefits [Member]      
Assumptions related to benefit costs:      
Discount rate 3.14% 3.24% 3.50%
Discount rate for interest on service cost [Member] | OPEB [Member]      
Assumptions related to benefit costs:      
Discount rate 3.76% 3.95% 4.17%