Property, Plant and Equipment (Regulated and Non-Regulated Generation and Distribution PP&E) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Electric generation, distribution assets and other	$ 28,491	$ 30,459
Accumulated depreciation	(9,449)	(9,962)
Net electric generation and distribution assets and other	19,042	20,497
Regulated Operation [Member]
Property, Plant and Equipment [Line Items]
Electric generation, distribution assets and other	11,818	13,103
Accumulated depreciation	(4,351)	(4,841)
Net electric generation and distribution assets and other	7,467	8,262
Unregulated Operation [Member]
Property, Plant and Equipment [Line Items]
Electric generation, distribution assets and other	16,673	17,356
Accumulated depreciation	(5,098)	(5,121)
Net electric generation and distribution assets and other	$ 11,575	$ 12,235