Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands		3 Months Ended			6 Months Ended				12 Months Ended
		Jun. 30, 2018		Jun. 30, 2017	Jun. 30, 2018		Jun. 30, 2017		Dec. 31, 2017
Operating activities
Net income		$ 176,852	[1]	$ 130,987	$ 351,789	[1],[2]	$ 254,680	[2]
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	[2]				25,033		21,593
Stock-based compensation	[2]				33,505		44,243
Provision for losses on accounts receivable	[2]				26,495		27,648
Amortization of deferred financing costs and discounts	[2]				2,678		3,800
Amortization of intangible assets	[2]				112,540		104,894
Amortization of premium on receivables	[2]				2,539		3,088
Deferred income taxes	[2]				(6,473)		(32,660)
Investment loss		0	[1]	2,354	0	[1],[2]	4,731	[2]
Other non-cash operating income	[2]				(104)		0
Changes in operating assets and liabilities (net of acquisitions):
Accounts and other receivables	[2]				(519,527)		(380,196)
Prepaid expenses and other current assets	[2]				(20,440)		(18,778)
Other assets	[2]				(15,418)		(15,050)
Accounts payable, accrued expenses and customer deposits	[2]				282,472		189,750
Net cash provided by operating activities	[2]				275,089		207,743
Investing activities
Acquisitions, net of cash acquired	[2]				(3,811)		(3,580)
Purchases of property and equipment		(19,400)		(17,804)	(34,614)	[2]	(32,600)	[2]
Other					(11,192)	[2]	(6,327)	[2]	$ (39,000)
Net cash used in investing activities	[2]				(49,617)		(42,507)
Financing activities
Proceeds from issuance of common stock	[2]				29,498		16,432
Repurchase of common stock	[2]				(380,651)		(52,393)
Borrowings on securitization facility, net	[2]				128,000		150,000
Principal payments on notes payable	[2]				(69,000)		(66,725)
Borrowings from revolver	[2]				774,019		90,000
Payments on revolver	[2]				(600,109)		(215,901)
Borrowings on swing line of credit, net	[2]				13,632		10,245
Other	[2]				(149)		537
Net cash used in financing activities	[2]				(104,760)		(67,805)
Effect of foreign currency exchange rates on cash	[2]				(66,144)		24,416
Net increase in cash and cash equivalents and restricted cash	[2]				54,568		121,847
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]	$ 1,185,438		$ 765,617	1,185,438		765,617		$ 1,130,870
Supplemental cash flow information
Cash paid for interest	[2]				73,303		68,431
Cash paid for income taxes	[2]				$ 112,982		$ 188,157

[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.

[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.