XML 73 R65.htm IDEA: XBRL DOCUMENT v2.4.0.8
PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS Part 13 (Details) (USD $)
 12 Months Ended 12 Months Ended
Sep. 30, 2013
Sep. 30, 2012
Sep. 30, 2011
Dec. 31, 2010
Aug. 01, 2007
Dec. 31, 2010
Laclede Gas [Member]
Aug. 01, 2007
Laclede Gas [Member]
Feb. 20, 2010
Missouri Gas Energy (MGE) [Member]
Sep. 30, 2013
Postretirement Plans [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]                  
Extent of Lump-sum payments recognized, percentage 100.00%                
Lump-sum payments recognized as settlements $ 79,484,000 $ 60,085,000 $ 2,300,000            
Implementation period used to calculate return on plan assets (in years) 4 years                
Gains or losses includible in cost amortized to extent exceeds benefit obligations or market-related value of plan assets, percentage. 10.00%                
Recovery in rates for the qualified pension plans base allowance           15,500,000 4,800,000 10,000,000  
Recovery in rates for postretirement benefit       9,500,000 7,600,000        
Anticipated Contributions to pension plans for qualified trust 24,000,000                
Anticipated contributions to pension plans for non-qualified plans 400,000                
Medical insurance available until age is reached after early retirement 65 years                
Amortization period for transition obligation excluded from postretirement benefit cost (in years) 20 years                
Anticipated contributions to the postretirement plans for qualified trusts                 19,200,000
Anticipated payment directly to participants in postretirement plan                 300,000
Current investment policy targets an asset allocation to equity securities                 60.00%
Investment policy targets asset allocation to debt securities                 40.00%
Other Plans [Abstract]                  
401(K) plans, cost of defined contributions $ 5,000,000 $ 3,800,000 $ 3,600,000