New And Significant Accounting Policies (Narrative) (Detail) (USD $) In Millions, unless otherwise specified			3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014 Cummulative Lease Payments And Investment Contributions [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Payments made under tax equity agreements			$ 363
Carrying Amount of Investments in Tax Equity Agreements	$ 93	$ 98