Income Taxes - Summary of Provision for Income Taxes and U.S. Federal Tax Rate (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2018		Sep. 30, 2017	Sep. 30, 2018	[1]	Sep. 30, 2017
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount [Abstract]
Computed tax expense at the U.S. federal tax rate	$ 49,889		$ 114,626
Foreign income tax differential	2,359		(9,247)
Excess tax benefits related to stock-based compensation	(7,562)		(4,360)
State taxes net of federal benefits	3,119		5,926
Foreign-sourced nontaxable income	(5,620)		1,558
Foreign withholding taxes1	4,578		3,065
GILTI tax, net of foreign tax credits	5,576		0
Valuation allowance on investment loss	0		16,718
Transition tax, net of foreign tax credits	(22,731)		0
Other1	4,804		(3,607)
Provision for income taxes	$ 79,874	[1]	$ 124,679	$ 188,579		$ 227,756
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	1.00%		(2.80%)
Excess tax benefits related to stock-based compensation	(3.20%)		(1.30%)
State taxes net of federal benefits	1.30%		1.80%
Foreign-sourced nontaxable income	(2.40%)		0.50%
Foreign withholding taxes1	1.90%		0.90%
GILTI tax, net of foreign tax credits	2.40%		0.00%
Valuation allowance on investment loss	(0.00%)		5.10%
Transition tax, net of foreign tax credits	(9.60%)		(0.00%)
Other1	2.00%		(1.10%)
Provision for income taxes	33.60%		38.10%

[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 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 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.