Income Taxes Details of Deferred Tax Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Current Deferred Tax Assets:
Step up in tax basis due to the exchange of LP Units for Class A Shares	$ 11,271	$ 9,214
Total Current Deferred Tax Asset	11,271	9,214
Long-term Deferred Tax Assets:
Depreciation and Amortization	20,604	14,673
Compensation and Benefits	31,735	25,958
Step up in tax basis due to the exchange of LP Units for Class A Shares	192,811	181,783
Other	21,396	17,043
Total Long-term Deferred Tax Assets	266,546	239,457
Long-term Deferred Tax Liabilities:
Goodwill, Investments and Other	14,933	10,008
Total Long-term Deferred Tax Liabilities	14,933	10,008
Net Long-term Deferred Tax Assets Before Valuation Allowance	251,613	229,449
Valuation Allowance	0	0
Net Long-term Deferred Tax Assets	$ 251,613	$ 229,449