SEGMENT AND GEOGRAPHIC INFORMATION (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
SEGMENT AND GEOGRAPHIC INFORMATION
Revenues:	$ 924,587	$ 1,015,473	$ 862,602
Revenues, net of interest and transaction-based expenses:	787,045	880,771	795,044
Long-lived Assets, as defined:	63,450	68,857
United States
SEGMENT AND GEOGRAPHIC INFORMATION
Revenues:	271,038	303,508	290,053
Revenues, net of interest and transaction-based expenses:	262,962	295,212	278,686
Long-lived Assets, as defined:	47,675	50,993
United Kingdom
SEGMENT AND GEOGRAPHIC INFORMATION
Revenues:	456,801	492,204	398,020
Revenues, net of interest and transaction-based expenses:	337,440	376,809	348,895
Long-lived Assets, as defined:	10,536	12,018
Other
SEGMENT AND GEOGRAPHIC INFORMATION
Revenues:	196,748	219,761	174,529
Revenues, net of interest and transaction-based expenses:	186,643	208,750	167,463
Long-lived Assets, as defined:	$ 5,239	$ 5,846

Revenues from agency commissions, principal transactions, clearing services, equity in earnings of unconsolidated subsidiaries, software, analytics and market data, interest income and other income, net of interest and transaction-based expenses.

No definition available.

+ Details

Name:	gfig_RevenuesNetOfInterestAndTransactionBasedExpenses
Namespace Prefix:	gfig_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Long-lived assets other than financial instruments, long-term customer relationships of a financial institution, mortgage and other servicing rights, deferred policy acquisition costs, and deferred tax assets.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 131

-Paragraph 38

-Subparagraph b(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

Name:	us-gaap_NoncurrentAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Aggregate revenue recognized during the period (derived from goods sold, services rendered, insurance premiums, or other activities that constitute an entity's earning process). For financial services companies, also includes investment and interest income, and sales and trading gains.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 5

+ Details

Name:	us-gaap_Revenues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration