Revenue Recognition - Disaggregated Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	$ 19,653	$ 61,342
Software [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	17,440	52,877
Software [Member] | Third Party Software [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	16,240	48,542
Software [Member] | Proprietary Software [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	1,200	4,335
Professional Engineering Service [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	2,213	8,465
North America [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	17,982	57,480
North America [Member] | Software [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	16,147	50,517
North America [Member] | Software [Member] | Third Party Software [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	15,615	46,867
North America [Member] | Software [Member] | Proprietary Software [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	532	3,650
North America [Member] | Professional Engineering Service [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	1,835	6,963
Europe [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	796	2,433
Europe [Member] | Software [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	520	1,380
Europe [Member] | Software [Member] | Third Party Software [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	520	1,380
Europe [Member] | Professional Engineering Service [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	276	1,053
Asia [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	875	1,429
Asia [Member] | Software [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	773	980
Asia [Member] | Software [Member] | Third Party Software [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	105	295
Asia [Member] | Software [Member] | Proprietary Software [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	668	685
Asia [Member] | Professional Engineering Service [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	102	449
Transferred at a point in time [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	17,276	53,058
Transferred at a point in time [Member] | Software [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	17,223	52,254
Transferred at a point in time [Member] | Software [Member] | Third Party Software [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	16,203	48,431
Transferred at a point in time [Member] | Software [Member] | Proprietary Software [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	1,020	3,823
Transferred at a point in time [Member] | Professional Engineering Service [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	53	804
Transferred over time [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	2,377	8,284
Transferred over time [Member] | Software [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	217	623
Transferred over time [Member] | Software [Member] | Third Party Software [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	37	111
Transferred over time [Member] | Software [Member] | Proprietary Software [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	180	512
Transferred over time [Member] | Professional Engineering Service [Member]
Disaggregation Of Revenue [Line Items]
Disaggregated revenue	$ 2,160	$ 7,661