Segment and Related Information - Reconciliation of Operating Income from Segments to Consolidated (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information
Total segment operating income	$ 49,656	$ 40,053	$ 124,890	$ 111,210
Other income, net	280	499	1,740	838
Income before income taxes	49,936	40,552	126,630	112,048
Operating segment and corporate non-segment
Segment Reporting Information
Total segment operating income	63,013	53,674	165,064	149,617
Segment reconciling items
Segment Reporting Information
Other income, net	280	499	1,740	838
Segment reconciling items | Acquired software
Segment Reporting Information
Amortization of intangibles assets	(7,965)	(7,975)	(23,998)	(22,645)
Segment reconciling items | Customer and trade name
Segment Reporting Information
Amortization of intangibles assets	$ (5,392)	$ (5,646)	$ (16,176)	$ (15,762)