Earnings Per Share - Summary of Earnings Per Share, Basic and Diluted (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2018		Jun. 30, 2017	Jun. 30, 2018		Jun. 30, 2017
Earnings Per Share [Abstract]
Net income	$ 176,852	[1]	$ 130,987	$ 351,789	[1],[2]	$ 254,680	[2]
Denominator for basic earnings per share (in shares)	89,169	[1]	92,013	89,466	[1]	92,060
Dilutive securities (in shares)	3,533		2,210	3,504		2,332
Denominator for diluted earnings per share (in shares)	92,702	[1]	94,223	92,970	[1]	94,392
Basic earnings per share (in dollars per share)	$ 1.98	[1]	$ 1.42	$ 3.93	[1]	$ 2.77
Diluted earnings per share (in dollars per share)	$ 1.91	[1]	$ 1.39	$ 3.78	[1]	$ 2.70

[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.