Significant Accounting Policies (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($) Project $ / shares shares	Sep. 30, 2018 USD ($) Project shares	Sep. 30, 2019 USD ($) Project Method Source $ / shares shares	Sep. 30, 2018 USD ($) Project shares	Feb. 26, 2019 USD ($)	Dec. 31, 2018 USD ($)
Accounting Policies [Line Items]
Number of product revenue sources | Method			2
Unbilled receivables	$ 76,100,000		$ 76,100,000			$ 57,000,000.0
Number of projects | Project	29	8	31	14
Percentage of total revenues	21.90%	15.70%	20.50%	14.00%
Percentage of product revenues	28.90%	23.10%	28.00%	20.30%
Number of service revenue sources | Source			2
Severance costs	$ 500,000		$ 4,000,000.0
Treasury stock shares (in shares) | shares	75,737,000	1,395,521,000	125,888,000	1,614,623,000
Average price of shares (in dollars per share) | $ / shares	$ 44.45		$ 42.60
Reclassified from engineering cost to product development cost		$ 4,800,000		$ 15,000,000.0
Reclassified from selling general and administrative cost to product cost of sales		700,000		2,300,000
Engineering cost	$ 3,900,000		$ 12,200,000
Quality assurance costs	700,000		2,300,000
Revenues	99,735,000		277,454,000
Net loss	(1,310,000)	(10,358,000)	(5,679,000)	(20,783,000)
Out-of-period adjustments
Accounting Policies [Line Items]
Net loss	(1,500,000)
Products
Accounting Policies [Line Items]
Revenues	81,851,000	$ 63,246,000	$ 224,518,000	$ 199,010,000
Products | Out-of-period adjustments
Accounting Policies [Line Items]
Revenues	$ 3,400,000
Common Stock
Accounting Policies [Line Items]
Shares authorized to be purchased (up to) (in shares)					$ 100,000,000
Treasury stock shares (in shares) | shares	75,737		125,888
Treasury stock, value of acquired shares	$ 3,400,000		$ 5,400,000