Income Taxes - Summary of Provision for Income Taxes and U.S. Federal Tax Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Computed “expected” tax expense	$ 229,976		$ 312,756	$ 225,022
Change in valuation allowance	25,193		18,289	11,952
Foreign income tax differential	9,921		(38,695)	(25,533)
State taxes net of federal benefits	20,480		12,884	9,439
Foreign-sourced nontaxable income	(28,861)		(8,836)	(13,659)
Foreign Withholding Tax	20,569		9,362	5,698
IRC Section 199 deduction	0		(8,844)	(7,731)
Excess Tax Benefits Related to Stock-Based Compensation	(19,255)		(18,058)	(11,974)
One-Time Transition Tax	0		195,779	0
Foreign Tax Credit - One-Time Transition Tax	17,385		(113,955)	0
Deferred Tax Effects	7,128		(209,965)	0
Sub-part F Income/GILTI	40,200		3,741	0
Foreign Tax Credits	(52,095)		0	0
Other	13,001		(1,068)	(2,680)
Total provision	$ 283,642	[1]	$ 153,390	$ 190,534
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Percent [Abstract]
Computed "expected" tax expense, rate	21.00%		35.00%	35.00%
Change in valuation allowance, rate	2.80%		2.00%	1.90%
Foreign income tax differential, rate	0.90%		(4.30%)	(4.00%)
State taxes net of federal benefits, rate	1.90%		1.40%	1.50%
Foreign-sourced nontaxable income, rate	(2.60%)		(1.00%)	(1.20%)
Foreign Withholding Tax, rate	1.90%		1.00%	0.00%
IRC Section 199 deduction, rate	(0.00%)		(1.00%)	(1.20%)
Excess tax benefits related to stock-based compensation, rate	(1.80%)		(2.00%)	(1.90%)
One-time transition tax, rate	0.00%		21.90%	0.00%
Foreign tax credit - one-time transition tax	1.60%		(12.80%)	0.00%
Deferred tax effects, rate	0.10%		(23.50%)	0.00%
Sub-part F Income/GILTI, rate	3.70%		0.40%	0.00%
Foreign tax credits, rate	(4.80%)		(0.00%)	(0.00%)
Other, rate	1.20%		0.10%	(0.40%)
Provision for income taxes, rate	25.90%		17.20%	29.70%

[1] Reflects the impact of the Company's adoption of Accounting Standards Update 2014-09, Revenue from Contracts with Customers (Topic 606) ("ASC 606") and related cost capitalization guidance, which was adopted by the Company on January 1, 2018 using the modified retrospective transition method. The adoption of ASC 606 resulted in an adjustment to retained earnings in our consolidated balance sheet for the cumulative effect of applying the standard, which included costs incurred to obtain a contract, as well as presentation changes in our statements of income, including the classification of certain amounts previously classified as merchant commissions and processing expense net with revenues. As a result of the application of the modified retrospective transition method, the Company's prior period results within its Form 10-K and quarterly reports on Form 10-Q will not be restated to reflect ASC 606.