Long-Term Debt	9 Months Ended
Jun. 30, 2011
Long-Term Debt [Abstract]
Long-Term Debt	NOTE 4. LONG-TERM DEBT UNSECURED NOTES Washington Gas issues unsecured Medium-Term Notes (MTNs) and private placement notes with individual terms regarding interest rates, maturities and call or put options. These notes can have maturity dates of one or more years from the date of issuance. On December 3, 2010, Washington Gas issued $75.0 million of 5.21% fixed MTNs with a thirty year maturity due December 3, 2040. The estimated effective cost of the notes, including consideration of issuance fees and hedge costs, is 5.96%. At June 30, 2011, Washington Gas had the capacity, under a shelf registration to issue up to $375.0 million of additional MTNs. At June 30, 2011 and September 30, 2010, outstanding MTNs and private placement notes were $660.0 million and $615.0 million, respectively. At June 30, 2011 and September 30, 2010, the weighted average interest rate on all MTNs and private placement notes was 5.91% and 6.04%, respectively.

Long-Term Debt

9 Months Ended

Jun. 30, 2011

NOTE 4. LONG-TERM DEBT

UNSECURED NOTES

Washington Gas issues unsecured Medium-Term Notes (MTNs) and private placement notes with individual terms regarding interest rates, maturities and call or put options. These notes can have maturity dates of one or more years from the date of issuance.

On December 3, 2010, Washington Gas issued $75.0 million of 5.21% fixed MTNs with a thirty year maturity due December 3, 2040. The estimated effective cost of the notes, including consideration of issuance fees and hedge costs, is 5.96%.

At June 30, 2011, Washington Gas had the capacity, under a shelf registration to issue up to $375.0 million of additional MTNs. At June 30, 2011 and September 30, 2010, outstanding MTNs and private placement notes were $660.0 million and $615.0 million, respectively. At June 30, 2011 and September 30, 2010, the weighted average interest rate on all MTNs and private placement notes was 5.91% and 6.04%, respectively.