Components of Other Operating Expenses (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Component of Operating Other Cost and Expense [Line Items]
Construction costs	$ 38		$ 26
Insurance subsidiary operating expenses	3	[1]	4	[1]
Other	(2)		(2)
Total other operating expenses	$ 39		$ 28

[1] Insurance subsidiary operating expenses are primarily comprised of incurred but not reported loss reserves, loss adjustment expenses and policy acquisition costs.