Basis of Presentation and Significant Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended	11 Months Ended
Feb. 28, 2019	Mar. 31, 2018	Nov. 30, 2018
Loans and Leases Receivable Disclosure [Line Items]
Receivables from brokers, dealers and clearing organizations	$ 4,537,200		$ 3,223,700
Receivables from customers of securities operations	1,597,000		2,017,100
Payables to brokers, dealers and clearing organizations	2,767,600		2,465,600
Payables to customers of securities operations	3,389,600		3,176,700
Cash paid during the year for:
Interest	399,350	$ 322,769
Income tax payments (refunds), net	7,205	$ (1,918)
Foursight Capital \| Automobile Loan
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Gross	$ 668,600		$ 648,700
Credit Concentration Risk \| Loans Receivable \| Prime \| Foursight Capital \| Automobile Loan
Loans and Leases Receivable Disclosure [Line Items]
Concentration risk, percentage	14.00%		13.00%
Credit Concentration Risk \| Loans Receivable \| Near-Prime \| Foursight Capital \| Automobile Loan
Loans and Leases Receivable Disclosure [Line Items]
Concentration risk, percentage	57.00%		57.00%
Credit Concentration Risk \| Loans Receivable \| Subprime \| Foursight Capital \| Automobile Loan
Loans and Leases Receivable Disclosure [Line Items]
Concentration risk, percentage	29.00%		30.00%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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