Benefit Plans - Schedule of Pension Plans' Fair Value Measurements (Details) (Pension Plans, Defined Benefit, USD $) In Thousands, unless otherwise specified	Aug. 31, 2013	Aug. 31, 2012	Aug. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	$ 730,628	$ 688,196	$ 540,822
Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	190,378	194,898
Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	667	2,588
Level 1 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	113,982	115,515
Level 1 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	75,729	76,795
Level 1 | Real estate funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value
Level 1 | Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value
Level 2
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	516,629	475,046
Level 2 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value		21,380
Level 2 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	80,619	289,286
Level 2 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	409,996	164,380
Level 2 | Partnership and joint venture interests
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	26,014
Level 2 | Real estate funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value
Level 2 | Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value
Level 3
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	23,621	18,252
Level 3 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value
Level 3 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value
Level 3 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	1,940
Level 3 | Real estate funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	18,156	16,257
Level 3 | Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	122	127
Estimate of Fair Value, Fair Value Disclosure [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	730,628	688,196
Estimate of Fair Value, Fair Value Disclosure [Member] | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	667	23,968
Estimate of Fair Value, Fair Value Disclosure [Member] | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	194,601	404,801
Estimate of Fair Value, Fair Value Disclosure [Member] | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	487,665	243,043
Estimate of Fair Value, Fair Value Disclosure [Member] | Partnership and joint venture interests
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	29,417
Estimate of Fair Value, Fair Value Disclosure [Member] | Real estate funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	18,156	16,257
Estimate of Fair Value, Fair Value Disclosure [Member] | Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans assets, fair value	$ 122	$ 127