Income Taxes - Summary of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Accounts receivable, principally due to the allowance for doubtful accounts	$ 8,518	$ 6,752
Accrued expenses not currently deductible for tax	6,734	442
Stock based compensation	40,081	37,274
Income tax credits	26,770	376
Net operating loss carry forwards	53,221	41,168
Investments	39,062	37,804
Accrued escheat	3,608	4,768
Other	4,240	12,604
Deferred tax assets before valuation allowance	182,234	141,188
Valuation allowance	(90,366)	(59,349)
Deferred tax assets, net	91,868	81,839
Deferred tax liabilities:
Intangibles—including goodwill	(483,361)	(508,958)
Basis difference in investment in foreign subsidiaries	(38,200)	(39,287)
Property and equipment, prepaid expenses and other	(59,101)	(50,705)
Deferred tax liabilities	(580,662)	(598,950)
Net deferred tax liabilities	$ (488,794)	$ (517,111)