Variable Interest Entities - Schedule of Sale and Deconsolidation of a Variable Interest Entity (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Variable Interest Entity [Line Items]
Proceeds from sale, net of transaction costs of $1	$ 108
Non-utility property, less accumulated depreciation	(388)	(605)
Long-term debt, including current portion	12,191	10,974
Gain on sale of solar electric production projects	(45)
California Solar [Member]
Variable Interest Entity [Line Items]
Proceeds from sale, net of transaction costs of $1	108
Non-utility property, less accumulated depreciation	(341)
Other assets, including working capital	(31)
Long-term debt, including current portion	217
Other liabilities	9
Gain on sale of solar electric production projects	(45)
Equity method investment upon deconsolidation	$ (83)