Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020 USD ($) Customer	Jun. 30, 2019 USD ($) Customer	Jun. 30, 2020 USD ($) Customer Vendor	Jun. 30, 2019 USD ($) Customer	Dec. 31, 2019 USD ($) Customer
Summary Of Significant Accounting Policies [Line Items]
Equity method investments	$ 0		$ 0		$ 0
Guarantee or other funding obligations under equity method investment	331,227,000		331,227,000		343,464,000
Earnings or losses from equity method investment	0	$ 0	0	$ 0
Revenue recognized from customer contracts	4,940,000
Remaining deferred revenues recognized			1,900,000
Note payable - related party	1,275,000		1,275,000		$ 1,275,000
Revenues	56,030,000	$ 65,016,000	122,003,000	$ 129,845,000
Number of customers with revenues greater than 10% | Customer		0		0
Number of customers with accounts receivable greater than 10% | Customer					0
Inventories finished goods and purchased parts	31,375,000		31,375,000		$ 33,379,000
Inventories raw materials	6,922,000		6,922,000		$ 6,502,000
Equity Method Investment, Guarantee or Other Funding [Member]
Summary Of Significant Accounting Policies [Line Items]
Guarantee or other funding obligations under equity method investment	$ 0	$ 0	$ 0	$ 0
Komatsu Ltd. [Member] | Customer Concentration Risk [Member] | Revenues [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage	10.40%
Schlumberger, Inc. [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of customers with accounts receivable greater than 10% | Customer			1
Schlumberger, Inc. [Member] | Accounts Receivable [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage			10.30%
Carrier Corporation [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of customers with revenues greater than 10% | Customer			1
Carrier Corporation [Member] | Customer Concentration Risk [Member] | Revenues [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage	21.10%		15.00%
Carrier Corporation and Komatsu Ltd. [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of customers with revenues greater than 10% | Customer	2
Sanmina Corporation [Member] | Customer Concentration Risk [Member] | Revenues [Member] | Mexico [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of vendors | Vendor			1
Revenues	$ 16,902,000	$ 17,388,000	$ 38,894,000	$ 35,312,000
Concentration risk percentage	92.30%	63.50%	88.50%	64.90%
Maximum [Member] | Revenues [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage		10.00%		10.00%
Maximum [Member] | Accounts Receivable [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage					10.00%
ASU 2014-09 [Member]
Summary Of Significant Accounting Policies [Line Items]
Warranty period			1 year
Estimated life of communicator			3 years
ASU 2014-09 [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Additional term of the agreement			2 years
ASU 2014-09 [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Additional term of the agreement			5 years