LONG-TERM DEBT (Narrative) (Details) (USD $)		12 Months Ended	1 Months Ended			12 Months Ended			12 Months Ended
	Sep. 30, 2012 interest_rate_swap_agreement	Sep. 30, 2012 3.4% Interest Rate Swaps Due 2014 [Member] interest_rate_swap_agreement	Jan. 31, 2012 Senior Notes [Member] 6.5% Senior Notes [Member]	Sep. 30, 2012 Senior Notes [Member] 6.5% Senior Notes [Member]	Sep. 30, 2011 Senior Notes [Member] 6.5% Senior Notes [Member]	Sep. 30, 2012 Senior Notes [Member] 6.5% Senior Notes [Member] Prior to Februrary 1, 2015 [Member]	Sep. 30, 2012 Senior Notes [Member] 6.5% Senior Notes [Member] Prior to February 1, 2016 [Member]	Sep. 30, 2012 Line of Credit [Member]	Sep. 30, 2012 Line of Credit [Member] 2011 Credit Facility [Member]	Sep. 30, 2011 Line of Credit [Member] 2011 Credit Facility [Member]	May 31, 2011 Line of Credit [Member] 2011 Credit Facility [Member]	Sep. 30, 2012 Line of Credit [Member] 2011 Credit Facility [Member] Maximum [Member]	May 31, 2011 Line of Credit [Member] 2011 Credit Facility [Member] Maximum [Member]	Sep. 30, 2012 Line of Credit [Member] 2011 Credit Facility [Member] Minimum [Member]	May 31, 2011 Line of Credit [Member] 2011 Credit Facility [Member] Minimum [Member]
Line of Credit Facility [Line Items]
Principal amount			$ 450,000,000	$ 450,000,000	$ 0
Interest rate			6.50%	6.50%
Debt instrument maturity year			2020
Net proceeds, after deducting underwriting discounts and estimated offering expenses			440,000,000
Indenture governing final judgments, maximum amount			50,000,000
Debt instrument redemption percentage						35.00%	100.00%
Credit facility outstanding								250,000,000	380,000,000	520,000,000
Credit facility maturity period											5 years
Credit facility capacity													1,300,000,000		750,000,000
Credit facility variable rate									Eurodollar
Credit facility basis spread on variable rate									2.50%
Credit facility effective percentage									3.20%
Credit facility commitment fee (per annum)									1.00%
Standby letters of credit									100,000
Credit facility additional funds borrowed									155,000,000
Credit facility funds available under credit facility									215,000,000
Incremental commitment increase											550,000,000
Leverage ratio												4.0
Debt to capitalization ratio									0.5
Interest expense coverage ratio														3.0
Minimum collateral maintenance percentage									150.00%
Number of interest rate swap agreements	5	5
Notional value, interest rate swap agreements	$ 50,000,000	$ 50,000,000
Interest rate fixed as result of interest rate swap hedges		3.40%