Benefit Plans - Schedule of Pension Plans' Fair Value Measurements (Details) - Pension Benefits - USD ($) $ in Thousands	Aug. 31, 2018	Aug. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	$ 829,616	$ 875,820
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	7,424	9,988
Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	692	459
Equity Securities: Common/collective trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	216,962	231,228
Fixed Income Securities: Common/collective trust [Member] [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	500,637	535,185
Partnership and joint venture interests
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	101,954	96,994
Other assets
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	1,947	1,966
Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	8,116	10,447
Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	7,424	9,988
Level 1 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	692	459
Level 1 | Equity Securities: Common/collective trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	0	0
Level 1 | Fixed Income Securities: Common/collective trust [Member] [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	0	0
Level 1 | Partnership and joint venture interests
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	0	0
Level 1 | Other assets
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	0	0
Level 2
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	0	0
Level 2 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	0	0
Level 2 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	0	0
Level 2 | Equity Securities: Common/collective trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	0	0
Level 2 | Fixed Income Securities: Common/collective trust [Member] [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	0	0
Level 2 | Partnership and joint venture interests
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	0	0
Level 2 | Other assets
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	0	0
Level 3
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	0	0
Level 3 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	0	0
Level 3 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	0	0
Level 3 | Equity Securities: Common/collective trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	0	0
Level 3 | Fixed Income Securities: Common/collective trust [Member] [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	0	0
Level 3 | Partnership and joint venture interests
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	0	0
Level 3 | Other assets
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	$ 0	$ 0