Organization, Business and Basis of Presentation (Details)	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2013 item
Organization, Business and Basis of Presentation
Number of business segments		2
Additional gross margin recognized as the result of revised cost estimates on transmission projects (as a percent)	1.30%	1.00%

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

No definition available.

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration