Unaudited Interim Financial Information (Table)

6 Months Ended

Mar. 31, 2012

Regulatory Assets And Liabilities Table [Abstract]

Regulatory assets and liabilities table

			March 31,		September 30,
			2012		2011
			(In thousands)
Regulatory assets:
	Pension and postretirement benefit costs	$	245,096	$	254,666
	Merger and integration costs, net		5,998		6,242
	Deferred gas costs		19,547		33,976
	Regulatory cost of removal asset		10,233		8,852
	Environmental costs		117		385
	Rate case costs		4,503		4,862
	Deferred franchise fees		333		379
	Other		8,861		3,534
		$	294,688	$	312,896
Regulatory liabilities:
	Deferred gas costs	$	15,232	$	8,130
	Regulatory cost of removal obligation		463,740		464,025
	Other		13,090		14,025
		$	492,062	$	486,180

Comprehensive Income Loss Table [Abstract]

Comprehensive income/loss table

		Three Months Ended				Six Months Ended
		March 31				March 31
		2012		2011		2012		2011
		(In thousands)
Net income		$	109,111	$	132,209	$	177,618	$	206,206
Unrealized holding gains on investments,
	net of tax expense of $1,203 and $477
	for the three months ended March 31,
	2012 and 2011 and of $1,717 and $932
	for the six months ended March 31, 2012
	and 2011		2,046		810		2,947		1,586
Amortization, unrealized gain and unwinding
	of treasury lock agreements, net of tax
	expense (benefit) of $9,042 and $(6,125)
	for the three months ended March 31, 2012
	and 2011 and $8,404 and $12,579 for the six
	month ended March 31, 2012 and 2011		15,396		(10,427)		14,309		21,420
Net unrealized gains (losses) on cash flow
	hedging transactions, net of tax expense
	(benefit) of $(3,399) and $2,573 for the three
	months ended March 31, 2012 and 2011 and
	$(13,996) and $9,190 for the six months
	ended March 31, 2012 and 2011		(5,315)		4,025		(21,890)		14,375
Comprehensive income		$	121,238	$	126,617	$	172,984	$	243,587

Accumulated Other Comprehensive Income Loss Table [Abstract]

Accumulated other comprehensive income/loss table

		March 31,		September 30,
		2012		2011
		(In thousands)
Accumulated other comprehensive income (loss):
	Unrealized holding gains on investments	$	5,505	$	2,558
	Treasury lock agreements		(19,848)		(34,157)
	Cash flow hedges		(38,751)		(16,861)
		$	(53,094)	$	(48,460)