XML 116 R91.htm IDEA: XBRL DOCUMENT v3.8.0.1
EMPLOYEE BENEFIT PLANS - REGULATORY ASSETS AND AOCI (Details) - USD ($)
$ in Thousands
 12 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2015
Pension      
Amounts amortized to net periodic costs:      
Net actuarial (loss) $ (8,827) $ (7,281) $ (6,985)
Prior service (cost) credit (111) (111) (111)
OPEB      
Amounts amortized to net periodic costs:      
Net actuarial (loss) (4,370) (3,274) (2,943)
Prior service (cost) credit 365 365 364
Regulatory Assets | Pension      
Regulatory Assets and Accumulated Other Comprehensive Income (Loss)      
Regulatory Assets, Balance at beginning of period 94,941 86,960  
Amounts arising during the period, Net actuarial loss (gain) (9,429) 13,696  
Amounts amortized to net periodic costs:      
Net actuarial (loss) (6,799) (5,607)  
Prior service (cost) credit (108) (108)  
Regulatory Assets, Balance at end of period 78,605 94,941 86,960
Regulatory Assets | OPEB      
Regulatory Assets and Accumulated Other Comprehensive Income (Loss)      
Regulatory Assets, Balance at beginning of period 59,147 50,737  
Amounts arising during the period, Net actuarial loss (gain) 5,211 11,274  
Amounts amortized to net periodic costs:      
Net actuarial (loss) (4,209) (3,175)  
Prior service (cost) credit 311 311  
Regulatory Assets, Balance at end of period 60,460 59,147 50,737
Accumulated Other Comprehensive Income (Loss) | Pension      
Regulatory Assets and Accumulated Other Comprehensive Income (Loss)      
Accumulated Other Comprehensive Income (Loss), Balance at beginning of period 28,436 25,640  
Amounts arising during the period, Net actuarial loss (gain) (6,990) 4,475  
Amounts amortized to net periodic costs:      
Net actuarial (loss) (2,028) (1,676)  
Prior service (cost) credit (3) (3)  
Accumulated Other Comprehensive Income (Loss), Balance at end of period 19,415 28,436 25,640
Accumulated Other Comprehensive Income (Loss) | OPEB      
Regulatory Assets and Accumulated Other Comprehensive Income (Loss)      
Accumulated Other Comprehensive Income (Loss), Balance at beginning of period 4,486 1,242  
Amounts arising during the period, Net actuarial loss (gain) 587 3,289  
Amounts amortized to net periodic costs:      
Net actuarial (loss) (160) (99)  
Prior service (cost) credit 54 54  
Accumulated Other Comprehensive Income (Loss), Balance at end of period $ 4,967 $ 4,486 $ 1,242