Supplemental Financial Information (Tables)

12 Months Ended

Dec. 31, 2014

Supplemental Financial Information [Abstract]

Schedule of Quarterly Financial Information [Table Text Block]

	Quarter Ended
	March 31, 2014		June 30, 2014		September 30, 2014		December 31, 2014
	(in thousands)
Total revenues	$	106,677	$	92,902	$	107,101	$	121,096
Net Income (loss) before income taxes	14,106		13,644		10,670		19,416
Income tax expense (benefit)	79		46		141		(125,210		)
Net income (loss) from continuing operations	14,027		13,598		10,529		144,626
Net Income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	4,187		5,216		4,006		2,155
Net income (loss) attributable to Cowen Group, Inc. stockholders	$	9,840	$	8,382	$	6,523	$	142,471
Earnings (loss) per share:
Basic	$	0.09	$	0.07	$	0.06	$	1.26
Diluted	$	0.08	$	0.07	$	0.05	$	1.21
Weighted average number of common shares:
Basic	115,680		115,569		114,969		113,492
Diluted	122,898		120,199		118,801		118,222

	Quarter Ended
	March 31, 2013			June 30, 2013		September 30, 2013			December 31, 2013
	(in thousands)
Total revenues	$	68,329		$	81,933	$	81,912		$	96,345
Net Income (loss) before income taxes	1,095			3,506		8,324			5,372
Income tax expense (benefit)	176			158		(46		)	169
Net income (loss) from continuing operations	919			3,348		8,370			5,203
Net Income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	3,495			2,255		4,759			2,684
Net income (loss) attributable to Cowen Group, Inc. stockholders	$	(2,576	)	$	1,093	$	3,611		$	2,519
Earnings (loss) per share:
Basic	$	(0.02	)	$	0.01	$	0.03		$	0.02
Diluted	$	(0.02	)	$	0.01	$	0.03		$	0.02
Weighted average number of common shares:
Basic	113,798			117,235		118,359			117,514
Diluted	113,798			120,901		122,708			123,573