Trading Securities Owned And Trading Securities Sold, But Not Yet Purchased (Components Of Trading Securities Owned And Trading Securities Sold, But Not Yet Purchased) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Trading securities	$ 746,213	$ 474,951
Trading securities pledged	352,283	393,888
Securities Owned [Member]
Trading securities	746,213	474,951
Securities Owned [Member] \| U.S. Government Agency Securities [Member]
Trading securities owned	144,286	66,424
Securities Owned [Member] \| U.S. Government Securities [Member]
Trading securities owned	8,059	32,845
Securities Owned [Member] \| Corporate Fixed Income Securities [Member]
Fixed income securities	391,981	244,535
Securities Owned [Member] \| Corporate Equity Securities [Member]
Equity securities	39,829	19,859
Securities Owned [Member] \| State And Municipal Securities [Member]
State and municipal securities	162,058	111,288
Securities Sold, But Not yet Purchased [Member]
Trading securities	369,886	266,833
Securities Sold, But Not yet Purchased [Member] \| U.S. Government Agency Securities [Member]
Trading securities owned	8,464	954
Securities Sold, But Not yet Purchased [Member] \| U.S. Government Securities [Member]
Trading securities owned	148,876	109,776
Securities Sold, But Not yet Purchased [Member] \| Corporate Fixed Income Securities [Member]
Fixed income securities	173,157	149,460
Securities Sold, But Not yet Purchased [Member] \| Corporate Equity Securities [Member]
Equity securities	39,284	6,060
Securities Sold, But Not yet Purchased [Member] \| State And Municipal Securities [Member]
State and municipal securities	$ 105	$ 583

Trading Securities Owned And Trading Securities Sold, But Not Yet Purchased (Components Of Trading Securities Owned And Trading Securities Sold, But Not Yet Purchased) (Details) (USD $)
In Thousands, unless otherwise specified

Sep. 30, 2012

Dec. 31, 2011

$ 746,213

$ 474,951

Trading securities pledged

352,283

393,888

Securities Owned [Member]

Trading securities

746,213

474,951

Securities Owned [Member] | U.S. Government Agency Securities [Member]

Trading securities owned

144,286

66,424

Securities Owned [Member] | U.S. Government Securities [Member]

Trading securities owned

8,059

32,845

Securities Owned [Member] | Corporate Fixed Income Securities [Member]

Fixed income securities

391,981

244,535

Securities Owned [Member] | Corporate Equity Securities [Member]

Equity securities

39,829

19,859

Securities Owned [Member] | State And Municipal Securities [Member]

State and municipal securities

162,058

111,288

Securities Sold, But Not yet Purchased [Member]

Trading securities

369,886

266,833

Securities Sold, But Not yet Purchased [Member] | U.S. Government Agency Securities [Member]

Trading securities owned

8,464

954

Securities Sold, But Not yet Purchased [Member] | U.S. Government Securities [Member]

Trading securities owned

148,876

109,776

Securities Sold, But Not yet Purchased [Member] | Corporate Fixed Income Securities [Member]

Fixed income securities

173,157

149,460

Securities Sold, But Not yet Purchased [Member] | Corporate Equity Securities [Member]

Equity securities

39,284

6,060

Securities Sold, But Not yet Purchased [Member] | State And Municipal Securities [Member]

State and municipal securities

$ 105

$ 583

- Definition

The total of financial instruments that are bought and held principally for the purpose of selling them in the near term (thus held for only a short period of time) or for debt and equity securities formerly categorized as available-for-sale or held-to-maturity which the entity held as of the date it opted to account for such securities at fair value. An enterprise may also categorize such a security as trading without the intent to sell it in the near term assuming the decision to categorize the security as trading occurred at acquisition.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.4)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

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-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26626-111562

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Trading Securities

-URI http://asc.fasb.org/extlink&oid=6526789

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 159

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Implementation Guide (Q and A)

-Number FAS115

-Paragraph 35

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

- Definition

Debt securities that are bought and held principally for the purpose of selling them in the near term (thus held for only a short period of time) or for debt securities formerly categorized as available-for-sale or held-to-maturity which the entity held as of the date it opted to account for such securities at fair value. An enterprise may also categorize such a security as trading without the intent to sell it in the near term assuming the decision to categorize the security as trading occurred at acquisition.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.4)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26626-111562

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-Publisher FASB

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-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.(a),1)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Trading Securities

-URI http://asc.fasb.org/extlink&oid=6526789

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 159

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Implementation Guide (Q and A)

-Number FAS115

-Paragraph 35

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

- Definition

Total common and preferred stock (which is not mandatorily redeemable, redeemable at the option of the holder, or in any other way classified as liability) equity securities that are bought and held principally for the purpose of selling them in the near term (thus held for only a short period of time) or for equity securities formerly categorized as available-for-sale or held-to-maturity which the entity held as of the date it opted to account for such securities at fair value. An enterprise may also categorize such a security as trading without the intent to sell it in the near term assuming the decision to categorize the security as trading occurred at acquisition.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.4)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26626-111562

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

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-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

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-Paragraph 1

-Subparagraph (SX 210.7-03.(a),1(b))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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-Name Statement of Financial Accounting Standard (FAS)

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Trading Securities

-URI http://asc.fasb.org/extlink&oid=6526789

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

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Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 159

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Implementation Guide (Q and A)

-Number FAS115

-Paragraph 35

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details