XML 58 R48.htm IDEA: XBRL DOCUMENT v3.3.1.900
Defined Benefit Pension and Other Postretirement Plans - Components of Net Periodic Pension Expense and Other Postretirement Benefit Costs (Details) - USD ($)
$ in Millions
 3 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Pension Benefits    
Defined Benefit Plan Disclosure    
Service cost $ 2.5 $ 2.4
Interest cost 6.6 6.3
Expected return on assets (8.0) (7.9)
Amortization of:    
Prior service cost (benefit) 0.1 0.1
Actuarial loss 2.7 2.5
Net benefit cost 3.9 3.4
Change in associated regulatory liabilities 0.0 0.0
Net expense 3.9 3.4
Other Postretirement Benefits    
Defined Benefit Plan Disclosure    
Service cost 0.2 0.2
Interest cost 0.2 0.2
Expected return on assets (0.2) (0.2)
Amortization of:    
Prior service cost (benefit) (0.1) (0.1)
Actuarial loss 0.0 0.0
Net benefit cost 0.1 0.1
Change in associated regulatory liabilities 0.9 0.9
Net expense $ 1.0 $ 1.0