XML 42 R23.htm IDEA: XBRL DOCUMENT v2.4.0.6
Transactions With Major Customers and Affiliates (Tables)
12 Months Ended
Dec. 31, 2012
Transactions With Major Customers And Affiliates [Abstract]  
ScheduleOfRevenueByMajorCustomersByReportingSegmentsTableTextBlock
    2012 2011 2010 
 Public Service Enterprise Group $ 127.4 $ 136.7 $ 130.0 
 National Grid   93.5   98.2   115.1