Income Taxes (Schedule Of Company's Deferred Tax Assets And Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Income Taxes [Abstract]
Current Deferred Tax Assets, Step up in tax basis due to the exchange of LP Units for Class A Shares	$ 8,621	$ 5,092
Total Current Deferred Tax Asset	8,621	5,092
Long-term Deferred Tax Assets, Depreciation and Amortization	13,180	5,793
Long-term Deferred Tax Assets, Compensation and Benefits	23,002	28,631
Long-term Deferred Tax Liabilities, Step up in tax basis due to the exchange of LP Units for Class A Shares	154,574	110,228
Long-term Deferred Tax Assets, Other	15,859	8,056
Total Long-term Deferred Tax Assets	206,615	152,708
Long-term Deferred Tax Liabilities, Goodwill and Investments	11,715	9,994
Total Long-term Deferred Tax Liabilities	11,715	9,994
Net Long-term Deferred Tax Assets Before Valuation Allowance	194,900	142,714
Valuation Allowance	(8,211)	(8,553)
Net Long-term Deferred Tax Assets	$ 186,689	$ 134,161