CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash provided by operating activities:
Net income (loss)	$ 3,630	$ 11,924	$ (10,323)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	31,926	33,602	31,312
Provision for doubtful accounts	441	305	166
Gain on sale of Guangzhou factory	0	(36,978)	0
Deferred income taxes	(1,779)	3,967	7,597
Shares issued for employee benefit plan	947	1,062	648
Employee and director stock-based compensation	8,845	8,820	11,943
Performance-based common stock warrants	1,997	163	683
Impairment of long-term assets	1,506	4,907	4,100
Changes in operating assets and liabilities:
Accounts receivable and contract assets	17,203	5,455	(22,192)
Inventories	(1,914)	(11,215)	(25,797)
Prepaid expenses and other assets	4,648	(587)	(4,477)
Accounts payable and accrued liabilities	14,233	(7,386)	10,970
Accrued income taxes	3,574	(1,184)	4,535
Net cash provided by operating activities	85,257	12,855	9,165
Cash provided by (used for) investing activities:
Proceeds from sale of Guangzhou factory	0	51,291	0
Acquisitions of property, plant and equipment	(21,313)	(20,142)	(40,384)
Refund of deposit received toward sale of Guangzhou factory	0	(5,053)	0
Acquisitions of intangible assets	(2,655)	(2,521)	(1,949)
Acquisition of net assets of Residential Control Systems, Inc.	0	0	(8,894)
Net cash provided by (used for) investing activities	(23,968)	23,575	(51,227)
Cash provided by (used for) financing activities:
Borrowings under line of credit	72,500	68,000	157,000
Repayments on line of credit	(106,000)	(104,500)	(68,987)
Proceeds from stock options exercised	448	864	1,442
Treasury stock purchased	(1,928)	(13,824)	(39,085)
Contingent consideration payments in connection with business combinations	(4,251)	(3,858)	0
Net cash provided by (used for) financing activities	(39,231)	(53,318)	50,370
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(963)	2,756	(803)
Net increase (decrease) in cash, cash equivalents and restricted cash	21,095	(14,132)	7,505
Cash, cash equivalents and restricted cash at beginning of year	53,207	67,339	59,834
Cash, cash equivalents and restricted cash at end of period	74,302	53,207	67,339
Supplemental cash flow information:
Income taxes paid	7,275	7,658	8,280
Interest paid	$ 4,403	$ 4,981	$ 2,751