Compensation and Benefits (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Compensation and benefits expense [Abstract]
Cash Compensation and Other Benefits	$ 7,347,000	$ 7,080,000	$ 14,834,000	$ 14,285,000
Non-Cash Compensation	665,000	1,180,000	1,351,000	2,363,000
Total Compensation and Benefits Expense	8,012,000	8,260,000	16,185,000	16,648,000
Compensation Arrangements [Line Items]
Non-Cash Compensation	665,000	1,180,000	1,351,000	2,363,000
Unrecorded compensation expense	2,000,000		2,000,000		2,100,000
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Liability related to the award	620,000		620,000		1,173,000
Delayed vesting cash awards 2012 [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Liability related to the award	800,000		800,000
Delayed vesting cash awards 2013 [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Liability related to the award	400,000		400,000
2006 Equity Incentive Plan [Member] | Common Class B [Member]
Compensation Arrangements [Line Items]
Shares granted (in shares)			53,116	6,000
Vesting period for units (in years)			4 years	4 years
2006 and 2007 Equity Incentive Plan [Member]
Compensation and benefits expense [Abstract]
Non-Cash Compensation	300,000	700,000	600,000	1,400,000
Compensation Arrangements [Line Items]
Non-Cash Compensation	300,000	700,000	600,000	1,400,000
Bonus plan [Member]
Compensation Arrangements [Line Items]
Compensation and benefits expense	$ 400,000	$ 500,000	$ 800,000	$ 1,000,000