Benefit Plans - Net Periodic Benefit Cost (Details) - USD ($)
$ in Thousands |
3 Months Ended |
9 Months Ended |
May 31, 2021 |
May 31, 2020 |
May 31, 2021 |
May 31, 2020 |
| Qualified Pension Benefits |
|
|
|
|
| Component of net periodic benefit costs: [Abstract] |
|
|
|
|
| Service cost |
$ 11,307
|
$ 10,538
|
$ 33,921
|
$ 31,613
|
| Interest cost |
4,141
|
5,431
|
12,422
|
16,292
|
| Expected return on assets |
(10,910)
|
(11,671)
|
(32,731)
|
(35,013)
|
| Prior service cost (credit) amortization |
45
|
45
|
134
|
134
|
| Actuarial loss (gain) amortization |
5,447
|
5,396
|
16,342
|
16,187
|
| Net periodic benefit cost (benefit) |
10,030
|
9,739
|
30,088
|
29,213
|
| Non-Qualified Pension Benefits |
|
|
|
|
| Component of net periodic benefit costs: [Abstract] |
|
|
|
|
| Service cost |
108
|
101
|
325
|
304
|
| Interest cost |
68
|
107
|
205
|
322
|
| Expected return on assets |
0
|
0
|
0
|
0
|
| Prior service cost (credit) amortization |
(28)
|
(28)
|
(85)
|
(85)
|
| Actuarial loss (gain) amortization |
53
|
25
|
159
|
74
|
| Net periodic benefit cost (benefit) |
201
|
205
|
604
|
615
|
| Other Benefits |
|
|
|
|
| Component of net periodic benefit costs: [Abstract] |
|
|
|
|
| Service cost |
297
|
262
|
890
|
787
|
| Interest cost |
123
|
187
|
369
|
560
|
| Expected return on assets |
0
|
0
|
0
|
0
|
| Prior service cost (credit) amortization |
(111)
|
(111)
|
(334)
|
(334)
|
| Actuarial loss (gain) amortization |
(341)
|
(348)
|
(1,024)
|
(1,044)
|
| Net periodic benefit cost (benefit) |
$ (32)
|
$ (10)
|
$ (99)
|
$ (31)
|