CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues
Agency commissions	$ 484,386	$ 561,026	$ 534,239
Principal transactions	211,159	235,580	215,563
Total brokerage revenues	695,545	796,606	749,802
Clearing services revenues	118,011	112,735	41,878
Interest income from clearing services	1,964	2,300	671
Equity in net earnings of unconsolidated businesses	8,569	10,466	3,974
Software, analytics and market data	84,153	73,620	60,637
Other income	16,345	19,746	5,640
Total revenues	924,587	1,015,473	862,602
Interest and transaction-based expenses
Transaction fees on clearing services	113,726	108,283	39,918
Transaction fees on brokerage services	22,843	24,541	27,213
Interest expense from clearing services	973	1,878	427
Total interest and transaction-based expenses	137,542	134,702	67,558
Revenues, net of interest and transaction-based expenses	787,045	880,771	795,044
Expenses
Compensation and employee benefits	546,501	627,368	558,248
Communications and market data	60,760	60,728	49,579
Travel and promotion	35,850	40,011	37,517
Rent and occupancy	23,667	24,664	22,413
Depreciation and amortization	36,624	38,943	34,431
Professional fees	23,238	27,413	25,949
Interest on borrowings	26,885	25,759	11,063
Other expenses	34,777	35,803	24,041
Total other expenses	788,302	880,689	763,241
(Loss) income before provision for income taxes	(1,257)	82	31,803
Provision for income taxes	8,387	2,647	5,884
Net (loss) income before attribution to non-controlling stockholders	(9,644)	(2,565)	25,919
Less: Net income attributable to non-controlling interests	309	616	304
GFI's net (loss) income	$ (9,953)	$ (3,181)	$ 25,615
(Loss) earnings per share available to common stockholders
Basic (in dollars per share)	$ (0.09)	$ (0.03)	$ 0.21
Diluted (in dollars per share)	$ (0.09)	$ (0.03)	$ 0.20
Weighted average shares outstanding
Basic (in shares)	116,014,202	118,334,995	120,275,918
Diluted (in shares)	116,014,202	118,334,995	125,522,128
Dividends declared per share of common stock (in dollars per share)	$ 0.25	$ 0.20	$ 0.45