The capitalized costs incurred during the period (excluded from amortization) to purchase, lease or otherwise acquire an unproved property, including costs of lease bonuses and options to purchase or lease properties, the portion of costs applicable to minerals when land including mineral rights is purchased in fee, brokers' fees, recording fees, legal costs, and other costs incurred in acquiring properties.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-10.(c)(7)(ii))

-URI http://asc.fasb.org/extlink&oid=21918352&loc=d3e511914-122862

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 10

-Paragraph c

-Subparagraph 3(ii)(A)

-Article 4

Name:	us-gaap_AcquisitionCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Financial Information By Business Segment - Additional Information (Detail) (Con Edison Development [Member], USD $) In Millions, unless otherwise specified	1 Months Ended
	Jul. 31, 2012 MW	Oct. 31, 2012 Subsequent Event [Member] Company	Jul. 31, 2012 Alpaugh [Member]	Jul. 31, 2012 Alpaugh [Member] Contingent consideration [Member]	Jul. 31, 2012 Alpaugh [Member] Construction work in progress [Member]	Jul. 31, 2012 Alpaugh [Member] Deposits relating to power purchase agreements [Member]	Jul. 31, 2012 Alpaugh [Member] Construction [Member]	Oct. 31, 2012 California [Member] Subsequent Event [Member] MW	Oct. 31, 2012 California [Member] Subsequent Event [Member] Construction work in progress [Member]	Oct. 31, 2012 California [Member] Subsequent Event [Member] Deposits relating to power purchase agreements [Member]	Oct. 31, 2012 California [Member] Subsequent Event [Member] Construction [Member]
Segment Reporting Information [Line Items]
Solar energy purchased	70							40
Purchase price of solar energy development company			$ 288	$ 2	$ 284	$ 4	$ 350	$ 51	$ 39	$ 12	$ 200
Number of companies purchased		2