Employee Benefit and Incentive Plans (Details)	9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011
Unvested share-based compensation, shares	1,213,051
1997 Director Plan Restricted Class A Common Stock
Beginning balance
Granted
Vested, deferred or forfeited
Unvested share-based compensation, shares
2007 Plan Restricted Class A Common Stock
Beginning balance	244,424
Granted	100,000
Vested, deferred or forfeited	(82,888)
Unvested share-based compensation, shares	261,536	[1]
2011 Plan Restricted Class A Common Stock
Beginning balance
Granted	275,000
Vested, deferred or forfeited
Unvested share-based compensation, shares	275,000	[1]
Restricted Class A Common Stock Plans
Beginning balance	244,424		32,785
Granted	375,000		300,000
Vested, deferred or forfeited	(82,888)
Unvested share-based compensation, shares	536,536	[1]	244,424
1997 Director Plan Stock Units
Beginning balance	68,544
Granted and deferred
Unvested share-based compensation, shares	68,544
2007 Plan Stock Units
Beginning balance	438,260
Granted and deferred	60,000
Unvested share-based compensation, shares	498,260
2011 Plan Stock Units
Beginning balance	55,531
Granted and deferred	54,180
Unvested share-based compensation, shares	109,711
Stock Units Plans
Beginning balance	562,335
Granted and deferred	114,180
Unvested share-based compensation, shares	676,515
1997 Director Plan
Unvested share-based compensation, shares	68,554
2007 Plan
Unvested share-based compensation, shares	759,796
2011 Plan
Unvested share-based compensation, shares	384,711

[1] Includes (i) 275,000 performance based awards that contingently vest upon the attainment of certain specified performance measures, and (ii) 250,000 time based awards that vest based upon an employee's continued employment on pre-established vesting dates.