Nature of Business and Summary of Significant Accounting Policies - Additional Information (Detail)		3 Months Ended	12 Months Ended			77 Months Ended
	Jan. 16, 2018 $ / shares	Dec. 31, 2017 USD ($) IncentivePlan	Dec. 31, 2017 USD ($) Customer IncentivePlan	Dec. 31, 2016 USD ($) Customer	Dec. 31, 2015 USD ($) Customer	Dec. 31, 2017 USD ($) IncentivePlan	Feb. 14, 2018 USD ($)	Jan. 31, 2017 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2008 USD ($)	Jan. 13, 1995 USD ($)
Summary of Significant Accounting Policy [Line Items]
Cash, uninsured amount		$ 83,700,000	$ 83,700,000			$ 83,700,000
Bonds payable, carrying amount		26,700,000	26,700,000			26,700,000				$ 50,000,000	$ 20,000,000
Bonds payable, fair value		26,700,000	$ 26,700,000			26,700,000
Number of single customer comprising more than 10% of revenue | Customer			2	3	3
Allowance for doubtful accounts		0	$ 0	$ 0		0
Period of warranty for product defects			90 days to five years
Liability for warranty obligations		$ 9,724,000	$ 9,724,000	8,548,000	$ 8,739,000	$ 9,724,000			$ 8,415,000
Number of stock incentive plans | IncentivePlan		2	2			2
Stock-based compensation expense			$ 7,433,000	6,695,000	6,712,000
Total compensation cost related to non-vested stock options, market-based PSUs, RSUs and restricted stock not yet recognized		$ 17,100,000	$ 17,100,000			$ 17,100,000
Recognition period of unvested compensation expense			2 years 10 months 24 days
Impairment losses recognized on long-lived assets			$ 0	0	0
Impairment losses recognized on goodwill and other intangible assets						0
Research and development costs			$ 130,434,000	124,804,000	129,876,000
Tax cuts and jobs act, incomplete accounting, estimated income tax expense		11,900,000
Tax cuts and jobs act, incomplete accounting, estimated write-down of deferred tax assets		9,200,000
Tax cuts and jobs act, incomplete accounting, change in tax rate estimate income tax expense related to unrepatriated foreign earnings		2,700,000
Percentage of sales taxes collected from customers			1.00%
Dividend payments			$ 17,400,000	17,600,000	$ 18,400,000
Retained earnings		922,178,000	922,178,000	921,942,000		922,178,000
ASU 2016-09 [Member]
Summary of Significant Accounting Policy [Line Items]
Increase in additional paid in capital								$ 100,000
Retained earnings								100,000
Subsequent Events [Member]
Summary of Significant Accounting Policy [Line Items]
Common stock dividends per share declared | $ / shares	$ 0.09
Dividend declaration date	Jan. 16, 2018
Dividend record date	Jan. 31, 2018
Dividend payment date	Feb. 14, 2018
Ex-dividend date	Jan. 30, 2018
Quarterly dividend payable subsequent to balance sheet date							$ 4,400,000
Prepaid Expenses and Other Current Assets [Member]
Summary of Significant Accounting Policy [Line Items]
Current deferred costs related to prepaid and other assets		11,400,000	11,400,000	10,700,000		11,400,000
Other Assets [Member]
Summary of Significant Accounting Policy [Line Items]
Non-current deferred costs related to other assets		2,800,000	2,800,000	$ 900,000		2,800,000
Performance-Based PSUs [Member]
Summary of Significant Accounting Policy [Line Items]
Stock-based compensation expense			$ 0
Recognition period of unvested compensation expense			3 years
Unrecognized compensation expense related to other than options		$ 11,400,000	$ 11,400,000			$ 11,400,000
Non-qualified Stock Options and RSUs [Member] | ASU 2016-09 [Member]
Summary of Significant Accounting Policy [Line Items]
Increase in deferred tax assets								$ 10,000
Minimum [Member]
Summary of Significant Accounting Policy [Line Items]
Amortization, estimated useful lives			9 months
Maintenance contract period			1 year
Maximum [Member]
Summary of Significant Accounting Policy [Line Items]
Amortization, estimated useful lives			14 years
Maintenance contract period			5 years
Building and Land Improvements [Member] | Minimum [Member]
Summary of Significant Accounting Policy [Line Items]
Property, plant and equipment, estimated useful lives			5 years
Building and Land Improvements [Member] | Maximum [Member]
Summary of Significant Accounting Policy [Line Items]
Property, plant and equipment, estimated useful lives			39 years
Office Machinery and Equipment [Member] | Minimum [Member]
Summary of Significant Accounting Policy [Line Items]
Property, plant and equipment, estimated useful lives			3 years
Office Machinery and Equipment [Member] | Maximum [Member]
Summary of Significant Accounting Policy [Line Items]
Property, plant and equipment, estimated useful lives			7 years
Engineering Machinery and Equipment [Member] | Minimum [Member]
Summary of Significant Accounting Policy [Line Items]
Property, plant and equipment, estimated useful lives			3 years
Engineering Machinery and Equipment [Member] | Maximum [Member]
Summary of Significant Accounting Policy [Line Items]
Property, plant and equipment, estimated useful lives			7 years
Computer Software [Member] | Minimum [Member]
Summary of Significant Accounting Policy [Line Items]
Property, plant and equipment, estimated useful lives			3 years
Computer Software [Member] | Maximum [Member]
Summary of Significant Accounting Policy [Line Items]
Property, plant and equipment, estimated useful lives			5 years
Credit Concentration Risk [Member]
Summary of Significant Accounting Policy [Line Items]
Percentage of accounts receivable accounted by each customers			63.80%	63.30%