Stockholders' Equity (Details)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Class A Common Stock Outstanding
Beginning balance	22,211,108		21,949,501		21,875,282
Issuance of class A common stock	6,690,466	[1],[2]		[1],[2]		[1],[2]
Issuance of restricted stock	375,000		300,000		16,875
Forfeiture of restricted stock	(4,042)				(9,925)
Purchase of shares for tax withholding upon vesting of restricted stock	(224,953)		(38,393)		(30,748)
Conversion of restricted stock to deferred units	(60,000)
Vesting of deferred units	278,935				98,017
Ending balance	29,266,514		22,211,108		21,949,501

[1] Excludes deferred stock units held by members of our board of directors of 898,000, 562,000, and 485,000 as of December 31, 2012, 2011, and 2010, respectively.

[2] Includes 5.0 million shares issued in December 2012 in conjunction with our Investment Management Business Sale and 1.7 million shares issued in November 2012 upon the exercise of outstanding warrants to purchase our class A common stock. See Note 1 for further discussion of our Investment Management Business Sale and see below in Note 6 for further discussion of the warrant exercise.