Stock-Based Compensation Plans - Summary of Nonvested Transaction Restricted Share Awards Issued under Stock Incentive Plan and Changes During Period (Detail) (S1 Corporation 2003 Stock Incentive Plan [Member], USD $)	3 Months Ended
	Mar. 31, 2015
S1 Corporation 2003 Stock Incentive Plan [Member]
Nonvested Restricted Share Awards
Beginning Balance	17,565
Forfeited	(2,910)
Ending Balance	14,655
Weighted-Average Grant Date Fair Value
Beginning Balance	$ 11.80
Forfeited	$ 11.80
Ending Balance	$ 11.80