Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands		3 Months Ended			9 Months Ended				12 Months Ended
		Sep. 30, 2018		Sep. 30, 2017	Sep. 30, 2018		Sep. 30, 2017		Dec. 31, 2017
Operating activities
Net income		$ 157,694	[1]	$ 202,823	$ 509,483	[1],[2]	$ 457,503	[2]
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	[2]				38,174		35,096
Stock-based compensation	[2]				54,207		68,897
Provision for losses on accounts receivable	[2]				43,520		35,949
Amortization of deferred financing costs and discounts	[2]				4,035		5,411
Amortization of intangible assets	[2]				165,002		158,897
Amortization of premium on receivables	[2]				4,202		4,738
Loss on extinguishment of debt		0		3,296	0		3,296
Deferred income taxes	[2]				(6,334)		(38,092)
Investment loss		7,147	[1]	47,766	7,147	[1],[2]	52,497	[2]
Gain on disposition of business					0		(174,984)
Other non-cash operating income	[2]				(140)		(49)
Changes in operating assets and liabilities (net of acquisitions):
Accounts and other receivables	[2]				(640,859)		(440,011)
Prepaid expenses and other current assets	[2]				(19,618)		(86,648)
Other assets	[2]				(19,922)		(15,378)
Accounts payable, accrued expenses and customer deposits	[2]				416,483		364,473
Net cash provided by operating activities	[2]				555,380		431,595
Investing activities
Acquisitions, net of cash acquired	[2]				(3,799)		(602,298)
Purchases of property and equipment		(21,698)		(16,859)	(56,312)	[2]	(49,459)	[2]
Proceeds from disposal of a business					0		316,501
Other					(11,192)	[2]	(6,327)	[2]	$ (39,000)
Net cash used in investing activities	[2]				(71,303)		(341,583)
Financing activities
Proceeds from issuance of common stock	[2]				48,322		20,192
Repurchase of common stock	[2]				(380,651)		(402,392)
Borrowings on securitization facility, net	[2]				120,000		203,000
Deferred financing costs paid and debt discount					(166)		(11,230)
Proceeds from issuance of notes payable					0		780,656
Principal payments on notes payable	[2]				(103,500)		(388,656)
Borrowings from revolver	[2]				834,019		845,000
Payments on revolver	[2]				(897,861)		(804,808)
Borrowings on swing line of credit, net	[2]				23,735		7,800
Other	[2]				(230)		537
Net cash (used in) provided by financing activities	[2]				(356,332)		250,099
Effect of foreign currency exchange rates on cash	[2]				(70,065)		34,390
Net increase in cash and cash equivalents and restricted cash	[2]				57,680		374,501
Cash and cash equivalents and restricted cash, beginning of period	[2]				1,130,870		643,770		643,770
Cash and cash equivalents and restricted cash, end of period	[2]	$ 1,188,550		$ 1,018,271	1,188,550		1,018,271		$ 1,130,870
Supplemental cash flow information
Cash paid for interest	[2]				113,785		79,144
Cash paid for income taxes	[2]				$ 162,563		$ 257,349

[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.

[2] Reflects the impact of the Company's adoption of Accounting Standards Update 2016-18, "Statement of Cash Flows (Topic 230)", which was adopted by the Company on January 1, 2018 and applied retrospectively to results for 2017. The adoption of Topic 230 resulted in the statement of cash flows presenting the changes in the total of cash, cash equivalents and restricted cash. As a result, the Company will no longer present transfers between cash and cash equivalents and restricted cash in the statement of cash flows.