Benefit Plans - Schedule of Pension Plans' Fair Value Measurements (Details) - Pension Plans, Defined Benefit - USD ($) $ in Thousands	Aug. 31, 2017	Aug. 31, 2016	Aug. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	$ 875,820	$ 883,265	$ 796,379
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	9,988	4,841
Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	459	507
Equity Securities: Common/collective trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	231,228	228,717
Fixed Income Securities: Common/collective trust [Member] [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	535,185	551,604
Partnership and joint venture interests
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	96,994	95,744
Other assets
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	1,966	1,852
Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	10,447	5,348
Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	9,988	4,841
Level 1 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	459	507
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