Summary of Significant Accounting Policies - Company's Accounts Receivable and Securitized Accounts Receivable (Detail) - USD ($) $ in Thousands	Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivables	$ 2,371,778		$ 2,277,042
Gross domestic securitized accounts receivable	886,000	[1]	811,000
Less allowance for doubtful accounts	(59,963)		(46,031)	$ (32,506)	$ (21,903)
Net accounts and securitized accounts receivable	2,311,815		2,231,011
Accounts Receivable Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivables	668,154		661,677
Accounts Receivable Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivables	$ 817,624		$ 804,365

[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 Form 10-K and quarterly reports on Form 10-Q will not be restated to reflect ASC 606.