Income Taxes - Details of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Assets:
Depreciation and Amortization	$ 26,319	$ 31,475
Compensation and Benefits	46,697	54,410
Step up in tax basis due to the exchange of LP Units for Class A Shares	106,360	202,257
Other	46,165	44,065
Total Deferred Tax Assets	225,541	332,207
Deferred Tax Liabilities:
Goodwill, Intangible Assets and Other	20,241	25,273
Total Deferred Tax Liabilities	20,241	25,273
Net Deferred Tax Assets Before Valuation Allowance	205,300	306,934
Valuation Allowance	(6,406)	(1,510)
Net Deferred Tax Assets	$ 198,894	$ 305,424