STATEMENTS OF CONSOLIDATED COMMON STOCKHOLDERS' EQUITY (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
STATEMENTS OF CONSOLIDATED COMMON STOCKHOLDERS' EQUITY
Natural gas, tax (in dollars)	$ 110,186	$ 30,047	$ 27,166
Interest rate, tax (in dollars)	5,720
Pension and other post-retirement benefits liability adjustment, tax (in dollars)	$ 2,752	$ 1,331	$ 3,733
Dividends (in dollars per share)	$ 0.88	$ 0.88	$ 0.88
Common stock, authorized shares	320,000,000	320,000,000
Preferred shares, authorized	3,000,000