Acquisitions - Purchase Price Allocation of PAY.ON (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill	$ 909,691	$ 909,691
PAY.ON [Member]
Business Acquisition [Line Items]
Cash and cash equivalents	1,627
Receivables	2,649
Other current assets	502
Total current assets acquired	4,778
Property and equipment	332
Goodwill	140,526
Other noncurrent assets	28
Total assets acquired	203,832
Accounts payable	1,058
Employee compensation	681
Other current liabilities	866
Total current liabilities acquired	2,605
Deferred income taxes	15,086
Total liabilities acquired	17,691
Net assets acquired	$ 186,141
Software [Member] | PAY.ON [Member]
Business Acquisition [Line Items]
Acquired intangible assets, weighted-average useful lives	5 years
Amortizable intangible assets	$ 34,150
Customer Relationships [Member] | PAY.ON [Member]
Business Acquisition [Line Items]
Acquired intangible assets, weighted-average useful lives	15 years
Amortizable intangible assets	$ 21,718
Trademarks | PAY.ON [Member]
Business Acquisition [Line Items]
Acquired intangible assets, weighted-average useful lives	5 years
Amortizable intangible assets	$ 2,300