Benefit Plans - Schedule of Pension Plans' Fair Value Measurements (Details) - Pension Plans, Defined Benefit - USD ($) $ in Thousands	Aug. 31, 2016	Aug. 31, 2015	Aug. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	$ 883,265	$ 796,379	$ 822,125
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	4,841	4,882
Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	507	91,619
Equity Securities: Common/collective trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	228,717	194,463
Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value		154,116
Fixed Income Securities: Common/collective trust [Member] [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	551,604	296,684
Partnership and joint venture interests
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	95,744	52,640
Other assets
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	1,852	1,975
Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	5,348	230,057
Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	4,841	4,882
Level 1 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	507	91,619
Level 1 | Equity Securities: Common/collective trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	0	0
Level 1 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value		133,556
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	20,560
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 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value		20,560
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 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value		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