Fair Value (Details) (Fair Value, Measurements, Recurring [Member], USD $) In Thousands, unless otherwise specified	Nov. 30, 2011	Aug. 31, 2011
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market investments	$ 128,391	$ 153,839
Derivative assets	49,465	52,858
Nonqualified benefit plan assets	48,680	49,357
Derivative liabilities	7,736	5,688
Nonqualified benefit plan liabilities	79,239	81,167
Fair Value, Inputs, Level 1 [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market investments	128,391	153,839
Derivative assets	1,918	2,329
Nonqualified benefit plan assets	48,680	49,357
Derivative liabilities	3,199	2,625
Nonqualified benefit plan liabilities	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market investments	0	0
Derivative assets	47,547	50,529
Nonqualified benefit plan assets	0	0
Derivative liabilities	4,537	3,063
Nonqualified benefit plan liabilities	79,239	81,167
Fair Value, Inputs, Level 3 [Member]
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market investments	0	0
Derivative assets	0	0
Nonqualified benefit plan assets	0	0
Derivative liabilities	0	0
Nonqualified benefit plan liabilities	$ 0	$ 0