Commitment and Contingencies - Outstanding Capital Commitments Associated with Investments in Unconsolidated Affiliates (Detail) (Corporate Joint Venture [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2014
Corporate Joint Venture [Member]
Other Commitments [Line Items]
Capital commitments, 2015	$ 5,164
Capital commitments, 2016	9,168
Capital commitments, 2017	36,891
Capital commitments, 2018	0
Capital commitments, 2019	27,242
Capital commitments, thereafter	0
Total capital commitments associated with investments in unconsolidated affiliated related to an EPC electrical transmission project	$ 78,465