Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Tax Assets:
Basis adjustments	$ 288,764	$ 339,133
Compensation and benefits	159,799	175,456
Net operating loss and tax credit carryforwards	249,509	239,959
Depreciation and amortization	1,764	1,537
Other	35,801	34,615
Gross deferred tax assets	735,637	790,700
Valuation allowance	(73,114)	(61,456)	$ (69,593)	$ (89,251)
Deferred tax assets (net of valuation allowance)	662,523	729,244
Deferred Tax Liabilities:
Depreciation and amortization	14,550	17,257
Compensation and benefits	9,816	23,251
Goodwill	26,124	21,749
Other	19,828	26,134
Deferred tax liabilities	70,318	88,391
Net deferred tax assets	$ 592,205	$ 640,853