Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred Tax Assets:
Basis adjustments	$ 339,133	$ 692,430
Compensation and benefits	175,456	197,750
Net operating loss and tax credit carryforwards	239,959	285,694
Depreciation and amortization	1,537	850
Other	34,615	53,895
Gross deferred tax assets	790,700	1,230,619
Valuation allowance	(61,456)	(69,593)	$ (89,251)	$ (1,044,152)
Deferred tax assets (net of valuation allowance)	729,244	1,161,026
Deferred Tax Liabilities:
Depreciation and amortization	17,257	26,539
Compensation and benefits	23,251	5,447
Goodwill	21,749	27,932
Other	26,134	34,499
Deferred tax liabilities	88,391	94,417
Net deferred tax assets	$ 640,853	$ 1,066,609