Nature of Business and Summary of Significant Accounting Policies - Additional Information (Detail)		12 Months Ended			65 Months Ended
	Jan. 17, 2017 $ / shares	Dec. 31, 2016 USD ($) Customer IncentivePlan	Dec. 31, 2015 USD ($) Customer	Dec. 31, 2014 USD ($)	Dec. 31, 2016 USD ($) IncentivePlan	Feb. 16, 2017 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2008 USD ($)	Jan. 13, 1995 USD ($)
Summary of Significant Accounting Policy [Line Items]
Cash, uninsured amount		$ 77,900,000			$ 77,900,000
Bonds payable, carrying amount		27,800,000			27,800,000			$ 50,000,000	$ 20,000,000
Bonds payable, fair value		$ 28,100,000			28,100,000
Number of customers accounting for 63.3 and 37.3 percent of accounts receivable | Customer		3	3
Allowance for doubtful accounts			$ 19,000
Period of warranty for product defects		90 days to five years
Liability for warranty obligations		$ 8,548,000	8,739,000	$ 8,415,000	$ 8,548,000		$ 8,977,000
Number of stock incentive plans | IncentivePlan		2			2
Performance period		3 years
Stock-based compensation expense		$ 6,695,000	6,712,000	8,563,000
Total compensation cost related to non-vested stock options, restricted stock units, performance stock units and restricted stock not yet recognized		$ 16,400,000			$ 16,400,000
Recognition period of non-vested compensation cost		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		$ 124,804,000	129,876,000	132,258,000
Percentage of sales taxes collected from customers		1.00%
Other income (expense) - Gain on previous acquisition of working capital		$ (651,000)	(1,465,000)	1,175,000
Dividend payments		$ 17,600,000	18,400,000	19,900,000
Dividend declaration date		Jan. 17, 2017
Dividend record date		Feb. 02, 2017
Dividend payment date		Feb. 16, 2017
Ex-dividend date		Jan. 31, 2017
Accounting Standards Update No. 2015-17 [Member]
Summary of Significant Accounting Policy [Line Items]
Non-current deferred tax assets		$ 17,300,000	18,900,000		17,300,000
Subsequent Events [Member]
Summary of Significant Accounting Policy [Line Items]
Common stock dividends per share declared | $ / shares	$ 0.09
Quarterly dividend payable subsequent to balance sheet date						$ 4,400,000
Nokia Siemens Networks [Member]
Summary of Significant Accounting Policy [Line Items]
Other income (expense) - Gain on previous acquisition of working capital				$ 2,400,000
Prepaid Expenses and Other Current Assets [Member]
Summary of Significant Accounting Policy [Line Items]
Deferred costs related to prepaid and other assets		$ 10,700,000	$ 5,200,000		$ 10,700,000
Minimum [Member]
Summary of Significant Accounting Policy [Line Items]
Amortization, estimated useful lives		9 months
Maintenance contract period		1 year
Minimum [Member] | Performance Stock Units (PSUs) [Member]
Summary of Significant Accounting Policy [Line Items]
Percentage of performance stock units granted		0.00%
Maximum [Member]
Summary of Significant Accounting Policy [Line Items]
Amortization, estimated useful lives		14 years
Maintenance contract period		5 years
Maximum [Member] | Performance Stock Units (PSUs) [Member]
Summary of Significant Accounting Policy [Line Items]
Percentage of performance stock units granted		150.00%
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		63.30%	37.30%		63.30%