Summary of Significant Accounting Principles - Additional Information (Detail)	3 Months Ended		12 Months Ended
	Mar. 31, 2016 USD ($) Customer	Mar. 31, 2015 USD ($) Customer	Dec. 31, 2015 USD ($) Customer
Summary Of Significant Accounting Policies [Line Items]
Equity method investments	$ 0		$ 0
Guarantee or other funding obligations under equity method investment	0
Losses from equity method investment	$ 0	$ 0
Number of customers with revenues greater than 10% | Customer	0	0
Number of customers with accounts receivable greater than 10% | Customer	1		1
Inventories finished goods and purchased parts	$ 18,005,000		$ 16,912,000
Inventories raw materials	$ 3,660,000		$ 3,800,000
Warranty period	1 year
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Caterpillar Inc. [Member]
Summary Of Significant Accounting Policies [Line Items]
Customers with accounts receivable greater than 10%	10.70%		11.60%