Comprehensive Income (Details) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Net income applicable to common stock	$ 2,952	$ 9,681	$ 147,612	$ 136,028
WGL Holdings, Inc.
Net income applicable to common stock	2,952	9,681	147,612	136,028
Net income before preferred stock dividend	3,282	10,011	148,602	137,018
Other comprehensive income (loss), net of taxes	146	777	421	608
Comprehensive income	3,098	10,458	148,033	136,636
Washington Gas Light Company
Net income applicable to common stock	(4,167)	(10,687)	106,953	120,609
Net income before preferred stock dividend	(3,837)	(10,357)	107,943	121,599
Other comprehensive income (loss), net of taxes	146	777	421	608
Comprehensive income	$ (3,691)	$ (9,580)	$ 108,364	$ 122,207