Income Taxes - Summary of Provision for Income Taxes and U.S. Federal Tax Rate (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2018		Jun. 30, 2017	Jun. 30, 2018	[1]	Jun. 30, 2017
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount [Abstract]
Computed tax expense at the U.S. federal tax rate	$ 48,547		$ 66,636
Foreign income tax differential	1,907		(7,473)
Excess tax benefits related to stock-based compensation	(5,946)		(937)
State taxes net of federal benefits	3,396		2,360
Foreign-sourced nontaxable income	(6,291)		(1,006)
Foreign withholding taxes	5,426		2,381
GILTI Tax, net of foreign tax credits	4,921		0
Other	2,363		(2,559)
Provision for income taxes	$ 54,323	[1]	$ 59,402	$ 108,705		$ 103,077
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Computed tax expense at the U.S. federal tax rate	21.00%		35.00%
Foreign income tax differential	0.80%		(3.90%)
Excess tax benefits related to stock-based compensation	(2.60%)		(0.50%)
State taxes net of federal benefits	1.50%		1.20%
Foreign-sourced nontaxable income	(2.70%)		(0.50%)
Foreign withholding taxes	2.40%		1.30%
GILTI Tax, net of foreign tax credits	2.10%		0.00%
Other	1.00%		(1.40%)
Provision for income taxes	23.50%		31.20%

[1] Reflects the impact of the Company's adoption of 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 effective 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 annual report on Form 10-K and quarterly reports on Form 10-Q will not be restated to reflect the impact of ASC 606. See footnote 1, "Summary of Significant Accounting Policies", in the accompanying notes to the unaudited consolidated financial statements.