Revenue Recognition (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Apr. 01, 2018	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of revenue	$ 46,284,000	$ 40,198,000
Gross margin	127,200,000	129,369,000
Operating income	30,147,000	34,596,000
Income before income tax expense	35,731,000	37,979,000
Income tax expense (benefit)	2,627,000	762,000
Net income	$ 33,104,000	$ 37,217,000
Basic (in dollars per share)	$ 0.19	$ 0.21
Diluted (in dollars per share)	$ 0.19	$ 0.21
Prepaid expenses and other current assets	$ 30,778,000		$ 34,000,000
Accrued income taxes	1,560,000		5,062,000
Deferred revenue and customer deposits	16,625,000		9,845,000
Retained earnings	670,754,000		646,214,000
Revenues	173,484,000	$ 169,567,000
Costs to fulfill a contract	4,960,000		$ 3,514,000
Change in Contract with Customer, Asset [Abstract]
Balance as of December 31, 2018	9,845,000
Increases to deferred revenue and customer deposits	12,015,000
Recognition of revenue	(5,292,000)
Foreign exchange rate changes	57,000
Balance as of March 31, 2019	16,625,000
Standard products and services
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	161,052,000	158,399,000
Application-specific customer solutions
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	12,432,000	11,168,000
Americas
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	65,156,000	59,217,000
Europe
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	59,657,000	56,203,000
Greater China
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	22,810,000	27,159,000
Other Asia
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	$ 25,861,000	$ 26,988,000