Benefit Plans - Schedule of Pension Plans' Fair Value Measurements (Details) - Pension Plans, Defined Benefit - USD ($) $ in Thousands	Aug. 31, 2015	Aug. 31, 2014	Aug. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	$ 796,379	$ 822,125	$ 730,628
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	4,882	4,218
Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	91,619	102,915
Equity Securities: Common/collective trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	194,463	48,400
Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	154,116	147,184
Fixed Income Securities: Common/collective trust [Member] [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	296,684	479,800
Partnership and joint venture interests
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	52,640	37,649
Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	1,975	1,959
Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	230,057	227,506
Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	4,882	4,218
Level 1 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	91,619	84,830
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	138,458
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 | Hedge funds
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	20,560	26,811
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	18,085
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	8,726
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 | Hedge funds
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	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 | Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	$ 0	$ 0