Statements of Consolidated Comprehensive Income (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statements of Consolidated Comprehensive Income
Natural gas, tax (benefit) expense	$ (12,984)	$ 41,436	$ (27,880)	$ (10,147)
Interest rate, tax expense	25	25	50	50
Pension and other post-retirement benefits liability adjustment, tax expense	$ 113	$ 306	$ 227	$ 613