Regulatory Assets, Liabilities, And Balancing Accounts (Current Regulatory Balancing Accounts, Net) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Regulatory Balancing Accounts Receivable [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	$ 1,655	$ 1,500
Regulatory Balancing Accounts Receivable [Member] | Electric Distribution [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	339	132
Regulatory Balancing Accounts Receivable [Member] | Utility Generation [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	248	48
Regulatory Balancing Accounts Receivable [Member] | Gas Distribution and Transmission [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	323	541
Regulatory Balancing Accounts Receivable [Member] | Energy Procurement [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	7	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	387	297
Regulatory Balancing Accounts Receivable [Member] | Electric Transmission [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	235	244
Regulatory Balancing Accounts Payable [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	908	645
Regulatory Balancing Accounts Payable [Member] | Electric Distribution [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	30	48
Regulatory Balancing Accounts Payable [Member] | Energy Procurement [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	102	13
Regulatory Balancing Accounts Payable [Member] | Public Purpose Programs [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	334	264
Regulatory Balancing Accounts Payable [Member] | Other Current Balancing Accounts [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	240	221
Regulatory Balancing Accounts Payable [Member] | Electric Transmission [Member]
Regulatory Assets [Line Items]
Total regulatory balancing accounts, net	$ 202	$ 99