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column '3 Months Ended Sep. 30, 2012' Process Flow-Through: Removing column '3 Months Ended Jun. 30, 2012' Process Flow-Through: Removing column '3 Months Ended Mar. 31, 2012' Process Flow-Through: Removing column '3 Months Ended Dec. 31, 2011' Process Flow-Through: Removing column '3 Months Ended Sep. 30, 2011' Process Flow-Through: Removing column '3 Months Ended Jun. 30, 2011' Process Flow-Through: Removing column '3 Months Ended Mar. 31, 2011' Process Flow-Through: 100040 - Statement - CONSOLIDATED STATEMENT OF CASH FLOWS Process Flow-Through: 100050 - Statement - CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS EQUITY Process Flow-Through: Removing column '3 Months Ended Dec. 31, 2012' Process Flow-Through: Removing column '3 Months Ended Sep. 30, 2012' Process Flow-Through: Removing column '3 Months Ended Jun. 30, 2012' Process Flow-Through: Removing column '3 Months Ended Mar. 31, 2012' Process Flow-Through: Removing column '3 Months Ended Dec. 31, 2011' Process Flow-Through: Removing column '3 Months Ended Sep. 30, 2011' Process Flow-Through: Removing column '3 Months Ended Jun. 30, 2011' Process Flow-Through: Removing column '3 Months Ended Mar. 31, 2011' Process Flow-Through: Removing column '12 Months Ended Dec. 31, 2012' Process Flow-Through: Removing column '12 Months Ended Dec. 31, 2011' Process Flow-Through: Removing column '12 Months Ended Dec. 31, 2010' Process Flow-Through: Removing column 'Apr. 09, 2012' Process Flow-Through: Removing column '3 Months Ended Dec. 31, 2012 The Connecticut Light And Power Company [Member]' Process Flow-Through: Removing column '3 Months Ended Sep. 30, 2012 The Connecticut Light And Power Company [Member]' Process Flow-Through: Removing column '3 Months Ended Jun. 30, 2012 The Connecticut Light And Power Company [Member]' Process Flow-Through: Removing column '3 Months Ended Mar. 31, 2012 The Connecticut Light And Power Company [Member]' Process Flow-Through: Removing column '3 Months Ended Dec. 31, 2011 The Connecticut Light And Power Company [Member]' Process Flow-Through: Removing column '3 Months Ended Sep. 30, 2011 The Connecticut Light And Power Company [Member]' Process Flow-Through: Removing column '3 Months Ended Jun. 30, 2011 The Connecticut Light And Power Company [Member]' Process Flow-Through: Removing column '3 Months Ended Mar. 31, 2011 The Connecticut Light And Power Company [Member]' Process Flow-Through: Removing column '12 Months Ended Dec. 31, 2012 The Connecticut Light And Power Company [Member]' Process Flow-Through: Removing column '12 Months Ended Dec. 31, 2011 The Connecticut Light And Power Company [Member]' Process Flow-Through: Removing column '12 Months Ended Dec. 31, 2010 The Connecticut Light And Power Company [Member]' Process Flow-Through: Removing column '3 Months Ended Dec. 31, 2012 Public Service Company Of New Hampshire [Member]' Process Flow-Through: Removing column '3 Months Ended Sep. 30, 2012 Public Service Company Of New Hampshire [Member]' Process Flow-Through: Removing column '3 Months Ended Jun. 30, 2012 Public Service Company Of New Hampshire [Member]' Process Flow-Through: Removing column '3 Months Ended Mar. 31, 2012 Public Service Company Of New Hampshire [Member]' Process Flow-Through: Removing column '3 Months Ended Dec. 31, 2011 Public Service Company Of New Hampshire [Member]' Process Flow-Through: Removing column '3 Months Ended Sep. 30, 2011 Public Service Company Of New Hampshire [Member]' Process Flow-Through: Removing column '3 Months Ended Jun. 30, 2011 Public Service Company Of New Hampshire [Member]' Process Flow-Through: Removing column '3 Months Ended Mar. 31, 2011 Public Service Company Of New Hampshire [Member]' Process Flow-Through: Removing column '12 Months Ended Dec. 31, 2012 Public Service Company Of New Hampshire [Member]' Process Flow-Through: Removing column '12 Months Ended Dec. 31, 2011 Public Service Company Of New Hampshire [Member]' Process Flow-Through: Removing column '12 Months Ended Dec. 31, 2010 Public Service Company Of New Hampshire [Member]' Process Flow-Through: Removing column '3 Months Ended Dec. 31, 2012 Western Massachusetts Electric Company [Member]' Process Flow-Through: Removing column '3 Months Ended Sep. 30, 2012 Western Massachusetts Electric Company [Member]' Process Flow-Through: Removing column '3 Months Ended Jun. 30, 2012 Western Massachusetts Electric Company [Member]' Process Flow-Through: Removing column '3 Months Ended Mar. 31, 2012 Western Massachusetts Electric Company [Member]' Process Flow-Through: Removing column '3 Months Ended Dec. 31, 2011 Western Massachusetts Electric Company [Member]' Process Flow-Through: Removing column '3 Months Ended Sep. 30, 2011 Western Massachusetts Electric Company [Member]' Process Flow-Through: Removing column '3 Months Ended Jun. 30, 2011 Western Massachusetts Electric Company [Member]' Process Flow-Through: Removing column '3 Months Ended Mar. 31, 2011 Western Massachusetts Electric Company [Member]' Process Flow-Through: Removing column '12 Months Ended Dec. 31, 2012 Western Massachusetts Electric Company [Member]' Process Flow-Through: Removing column '12 Months Ended Dec. 31, 2011 Western Massachusetts Electric Company [Member]' Process Flow-Through: Removing column '12 Months Ended Dec. 31, 2010 Western Massachusetts Electric Company [Member]' Process Flow-Through: Removing column '3 Months Ended Dec. 31, 2012 NSTAR Electric Company [Member]' Process Flow-Through: Removing column '3 Months Ended Sep. 30, 2012 NSTAR Electric Company [Member]' Process Flow-Through: Removing column '3 Months Ended Jun. 30, 2012 NSTAR Electric Company [Member]' Process Flow-Through: Removing column '3 Months Ended Mar. 31, 2012 NSTAR Electric Company [Member]' Process Flow-Through: Removing column '3 Months Ended Dec. 31, 2011 NSTAR Electric Company [Member]' Process Flow-Through: Removing column '3 Months Ended Sep. 30, 2011 NSTAR Electric Company [Member]' Process Flow-Through: Removing column '3 Months Ended Jun. 30, 2011 NSTAR Electric Company [Member]' Process Flow-Through: Removing column '3 Months Ended Mar. 31, 2011 NSTAR Electric Company [Member]' Process Flow-Through: Removing column '12 Months Ended Dec. 31, 2012 NSTAR Electric Company [Member]' Process Flow-Through: Removing column '12 Months Ended Dec. 31, 2011 NSTAR Electric Company [Member]' Process Flow-Through: Removing column '12 Months Ended Dec. 31, 2010 NSTAR Electric Company [Member]' nu-20121231.xml nu-20121231.xsd nu-20121231_cal.xml nu-20121231_def.xml nu-20121231_lab.xml nu-20121231_pre.xml true true