COMMITMENTS AND CONTINGENT LIABILITIES - CAPITAL EXPENDITURES (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Mar. 31, 2013
Gas Distribution [Member]
Long-term Purchase Commitment [Line Items]
Estimated capital expenditures	$ 145.8
Estimated capital expenditures subsequent fiscal year	119.9
Capital expenditures paid and accrued	64.9
SAFE Related Expenditures [Member]
Long-term Purchase Commitment [Line Items]
Estimated capital expenditures	27.7
Estimated capital expenditures subsequent fiscal year	43.4
Capital expenditures paid and accrued	9.0
AIP II Construction Costs [Member]
Long-term Purchase Commitment [Line Items]
Capital expenditures paid and accrued	10.2
Natural Disasters and Other Casualty Events [Member]
Long-term Purchase Commitment [Line Items]
Capital expenditures paid and accrued	24.1
Natural Disasters and Other Casualty Events [Member] | Minimum [Member]
Long-term Purchase Commitment [Line Items]
Estimated capital expenditures	26.0
Loss contingency, range of possible loss	30
Natural Disasters and Other Casualty Events [Member] | Maximum [Member]
Long-term Purchase Commitment [Line Items]
Estimated capital expenditures	30.0
Loss contingency, range of possible loss	40
Solar Related Expenditures [Member]
Long-term Purchase Commitment [Line Items]
Capital expenditures paid and accrued	48.9
Payments to acquire productive assets	24.9
Solar Related Expenditures [Member] | Minimum [Member]
Long-term Purchase Commitment [Line Items]
Estimated capital expenditures	60.0
Solar Related Expenditures [Member] | Maximum [Member]
Long-term Purchase Commitment [Line Items]
Estimated capital expenditures	90.0
Solar Related Expenditures Land Only [Member] | Minimum [Member]
Long-term Purchase Commitment [Line Items]
Estimated capital expenditures subsequent fiscal year	70.0
Solar Related Expenditures Land Only [Member] | Maximum [Member]
Long-term Purchase Commitment [Line Items]
Estimated capital expenditures subsequent fiscal year	$ 90.0