XML 47 R28.htm IDEA: XBRL DOCUMENT  v2.3.0.11
Income Tax (tables)
6 Months Ended
Jun. 30, 2011
Income Tax Expense Benefit Abstract  
Effective Tax Rate Reconciliation
  June 30,
 2011  2010 
Federal statutory tax rate 35.0%  35.0%
Increase (decrease):     
 Current state income tax, net of federal tax benefit 4.5%  4.8%
 Amortization of investment and energy tax credits (0.4)%  (0.4)%
 Differences required to be flowed-through by regulatory commissions 1.6%  1.4%
 Gains on company and trust-owned life insurance (0.6)%  (0.4)%
 Other - net 0.3%  0.1%
Effective income tax rate 40.4%  40.5%