Notes Payable and Long-Term Debt - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Sep. 30, 2015	Aug. 31, 2020	Aug. 31, 2019	Aug. 31, 2018	Aug. 14, 2020	Jun. 26, 2020	Jun. 25, 2020	Sep. 04, 2018
Debt Instrument [Line Items]
Interest expense		$ 116,977	$ 167,065	$ 149,202
Long-term Debt, Fair Value		1,900,000
Notes payable		1,575,491	2,156,108
Long-term Debt		1,750,947
Capitalized Interest		(10,900)	(9,400)	$ (6,700)
Long-term debt repaid		25,400
Line of Credit Facility, Current Borrowing Capacity		2,750,000
Principal Amount Outstanding of Loans Held-in-portfolio		423,000
maximum availability under securitization		500,000				$ 500,000	$ 700,000
Notes Purchase Agreement					$ 375,000
increase to maximum availability under securitization		600,000
Revolving credit facility
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity		$ 100,000
Unsecured debt | Minimum
Debt Instrument [Line Items]
Interest rate		0.00%
Unsecured debt | Maximum
Debt Instrument [Line Items]
Interest rate		10.00%
Five-year revolving facilities | Line of credit | Revolving credit facility
Debt Instrument [Line Items]
Line of credit facility, amount outstanding		$ 345,000	335,000
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 | Maximum
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.55%
Uncommitted lines of credit | Line of credit | Revolving credit facility
Debt Instrument [Line Items]
Long-term Line of Credit, Noncurrent		$ 318,400
Other international subsidiaries, lines of credit | Line of credit | Revolving credit facility
Debt Instrument [Line Items]
Line of credit facility, amount outstanding		69,700
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	150,000
Private placement, payable in equal installments beginning in 2017 through 2021 | Unsecured debt
Debt Instrument [Line Items]
Long-term Debt		$ 20,000	40,000
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		34,709	18,601
Notes Payable, Other Payables [Member] | Notes Payable, Other Payables [Member] | Revolving credit facility
Debt Instrument [Line Items]
Notes payable		763,215	$ 1,330,550
Recourse loan commitments | Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Short-term bank loans and notes payable current borrowing capacity		150,000
Notes payable		$ 133,300
Interest rate		1.45%
Short-Term Notes Payable, Surplus Funds Program [Member] | Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Notes payable		$ 134,900
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