Segment Information - Revenues, by Product Line (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue from External Customer [Line Items]
Revenues	$ 326,395	$ 225,735	$ 240,599	$ 231,462	$ 342,730	$ 216,975	$ 219,930	$ 226,066	$ 1,024,191	$ 1,005,701	$ 1,045,977
Retail Payments [Member]
Revenue from External Customer [Line Items]
Revenues									428,583	422,262	416,998
Bill Payments [Member]
Revenue from External Customer [Line Items]
Revenues									271,421	255,540	241,949
Digital Channels [Member]
Revenue from External Customer [Line Items]
Revenues									94,036	124,630	219,698
Payments Risk Management [Member]
Revenue from External Customer [Line Items]
Revenues									80,326	67,649	66,386
Merchant Payments [Member]
Revenue from External Customer [Line Items]
Revenues									76,953	64,626	49,064
Real Time Payments [Member]
Revenue from External Customer [Line Items]
Revenues									$ 72,872	$ 70,994	$ 51,882