Regulatory Assets, Liabilities, And Balancing Accounts (Current Regulatory Balancing Accounts, Net) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Regulatory Balancing Accounts Receivable [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	$ 1,478	$ 1,500
Regulatory Balancing Accounts Receivable [Member] | Electric Distribution [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	0	132
Regulatory Balancing Accounts Receivable [Member] | Utility Generation [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	0	48
Regulatory Balancing Accounts Receivable [Member] | Gas Distribution and Transmission [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	654	541
Regulatory Balancing Accounts Receivable [Member] | Energy Procurement [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	135	132
Regulatory Balancing Accounts Receivable [Member] | Public Purpose Programs [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	116	106
Regulatory Balancing Accounts Receivable [Member] | Other Current Balancing Accounts [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	391	297
Regulatory Balancing Accounts Receivable [Member] | Electric Transmission [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	182	244
Regulatory Balancing Accounts Payable [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	1,328	645
Regulatory Balancing Accounts Payable [Member] | Electric Distribution [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	197	0
Regulatory Balancing Accounts Payable [Member] | Utility Generation [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	150	0
Regulatory Balancing Accounts Payable [Member] | Gas Distribution and Transmission [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	0	48
Regulatory Balancing Accounts Payable [Member] | Energy Procurement [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	131	13
Regulatory Balancing Accounts Payable [Member] | Public Purpose Programs [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	426	264
Regulatory Balancing Accounts Payable [Member] | Other Current Balancing Accounts [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	282	221
Regulatory Balancing Accounts Payable [Member] | Electric Transmission [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	$ 142	$ 99