Interest Income And Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Interest Income Expense Net [Abstract]
Bank loans, net	$ 54,006	$ 35,484	$ 147,495	$ 91,517
Investment securities	48,072	27,161	136,123	73,968
Margin balances	9,919	7,438	27,124	24,135
Inventory	4,371	4,895	12,953	13,912
Other	1,494	(97)	4,071	(44)
Total interest income	117,862	74,881	327,766	203,488
Senior notes	8,655	12,164	24,935	28,518
Bank deposits	4,770	1,732	8,424	5,475
Federal Home Loan Bank advances	1,255	1,896	5,771	5,288
Other	2,945	3,591	11,035	11,475
Total interest expense	$ 17,625	$ 19,383	$ 50,165	$ 50,756

Interest income from inventory.

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- Definition

Margin balances.

+ References

No definition available.

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- Definition

Other interest and dividend income expense net.

+ References

No definition available.

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- Definition

Amount of operating dividend and interest income, including amortization and accretion of premiums and discounts, on available-for-sale securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.2)
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 35
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=82895926&loc=d3e24721-111560

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The aggregate interest and fee income generated by: (1) loans the Entity has positive intent and ability to hold for the foreseeable future, or until maturity or payoff, including commercial and consumer loans, whether domestic or foreign, which may consist of: (a) industrial and agricultural; (b) real estate; and (c) real estate construction loans; (d) trade financing; (e) lease financing; (f) home equity lines-of-credit; (g) automobile and other vehicle loans; and (h) credit card and other revolving-type loans and (2) loans and leases held-for-sale which may include mortgage loans, direct financing, and sales-type leases.

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Amount of the cost of borrowed funds accounted for as interest expense.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391

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-Publisher FASB
-Name Accounting Standards Codification
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-Subparagraph (SX 210.9-04.9)
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Amount of the cost of borrowed funds accounted for as interest expense for debt.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
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-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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The aggregate interest expense incurred on all domestic deposits.

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Interest expense incurred during the reporting period on short-term borrowings associated with Federal Home Loan Bank and Federal Reserve Bank advances.

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No definition available.

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- Definition

Amount of interest expense classified as other.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624177-113959

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Amount of operating interest income, including, but not limited to, amortization and accretion of premiums and discounts on securities.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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