Notes Payable and Long-Term Debt - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Sep. 30, 2015	Aug. 31, 2019	Aug. 31, 2018	Aug. 31, 2017	Sep. 04, 2018
Debt Instrument [Line Items]
Interest expense		$ 167,065	$ 149,202	$ 171,239
Long-term Debt, Fair Value		1,900,000
Notes payable		2,156,108	2,272,196
Long-term Debt		1,754,752
Capitalized Interest		(9,400)	(6,700)	$ (6,900)
Long-term debt repaid		153,600
Line of Credit Facility, Current Borrowing Capacity		$ 2,750,000
Unsecured debt | Minimum
Debt Instrument [Line Items]
Interest rate		1.30%
Unsecured debt | Maximum
Debt Instrument [Line Items]
Interest rate		15.25%
Five-year revolving facilities | Line of credit | Revolving credit facility
Debt Instrument [Line Items]
Line of credit facility, amount outstanding		$ 335,000	0
Debt Instrument, Term		5 years
Line of Credit Facility, Current Borrowing Capacity		$ 2,750,000
Five-year revolving facilities | Line of credit | Revolving credit facility | Minimum
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		0.00%
Five-year revolving facilities | Line of credit | Revolving credit facility | Maximum
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.45%
Three-year revolving facility | Line of credit | Revolving credit facility
Debt Instrument [Line Items]
Debt Instrument, Term		3 years
Line of Credit Facility, Current Borrowing Capacity		$ 315,000
Uncommitted lines of credit | Line of credit | Revolving credit facility
Debt Instrument [Line Items]
Long-term Line of Credit, Noncurrent		342,700
Other international subsidiaries, lines of credit | Line of credit | Revolving credit facility
Debt Instrument [Line Items]
Line of credit facility, amount outstanding		155,800
Line Of Credit, Collateralized Amount		13,800
Repurchase Facility [Member] | Subordinated Debt [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity					$ 150,000
Line of Credit Facility, Fair Value of Amount Outstanding		150,000
Master participation agreements | Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Short-term bank loans and notes payable current borrowing capacity		5,000
Notes payable		$ 2,300
Master participation agreements | Notes Payable, Other Payables [Member] | Minimum
Debt Instrument [Line Items]
Interest rate		4.19%
Term loans from cooperative and other banks | Line of credit | Revolving credit facility
Debt Instrument [Line Items]
Interest rate
Private placement, payable in equal installments beginning in 2014 through 2018 | Unsecured debt
Debt Instrument [Line Items]
Interest rate		6.18%
Debt Instrument, Face Amount		$ 400,000
Private placement, payable in installments through 2018 | Unsecured debt
Debt Instrument [Line Items]
Interest rate		5.60%
Debt Instrument, Face Amount		$ 60,000
Private placement, payable in equal installments beginning in 2014 through 2018 | Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Interest rate		5.78%
Debt Instrument, Face Amount		$ 50,000
Private placement, payable in equal installments beginning in 2017 through 2021 | Unsecured debt
Debt Instrument [Line Items]
Long-term Debt		$ 40,000	60,000
Private placement, payable in equal installments beginning in 2017 through 2021 | Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Interest rate		4.00%
Debt Instrument, Face Amount		$ 100,000
Other notes and contracts | Secured debt
Debt Instrument [Line Items]
Long-term Debt		18,601	32,607
Notes Payable, Other Payables [Member] | Notes Payable, Other Payables [Member] | Revolving credit facility
Debt Instrument [Line Items]
Notes payable		1,330,550	$ 1,437,264
Recourse loan commitments | Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Short-term bank loans and notes payable current borrowing capacity		65,800
Notes payable		$ 42,300
Interest rate		3.36%
Short-Term Notes Payable, Surplus Funds Program [Member] | Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Notes payable		$ 63,800
Short-Term Notes Payable, Surplus Funds Program [Member] | Notes Payable, Other Payables [Member] | Minimum
Debt Instrument [Line Items]
Interest rate		0.35%
Short-Term Notes Payable, Surplus Funds Program [Member] | Notes Payable, Other Payables [Member] | Maximum
Debt Instrument [Line Items]
Interest rate		1.40%
Committed Term Loans, September 2015 [Member] | Secured debt
Debt Instrument [Line Items]
Debt Instrument, Term	10 years
Debt Instrument, Face Amount		$ 600,000
Long-term Debt		$ 236,000