CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash provided by operating activities:
Net income (loss)	$ (10,323)	$ 20,384	$ 29,173
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	31,312	26,967	20,452
Provision for doubtful accounts	166	183	299
Provision for inventory write-downs	4,119	3,806	3,382
Deferred income taxes	7,597	(1,637)	(5,348)
Tax benefit from exercise of stock options and vested restricted stock	0	2,007	3,069
Excess tax benefit from stock-based compensation	0	(1,970)	(2,619)
Shares issued for employee benefit plan	648	913	868
Employee and director stock-based compensation	11,943	10,324	7,913
Performance-based common stock warrants	683	2,728	0
Impairment of China factory equipment	4,100	0	0
Changes in operating assets and liabilities:
Restricted cash	4,623	0	(4,623)
Accounts receivable	(22,192)	(3,882)	(29,407)
Inventories	(29,916)	(14,800)	(31,877)
Prepaid expenses and other assets	(4,477)	(772)	774
Accounts payable and accrued expenses	10,970	10,451	33,309
Accrued income taxes	4,535	(5,159)	729
Net cash provided by operating activities	13,788	49,543	26,094
Cash used for investing activities:
Acquisitions of property, plant, and equipment	(40,384)	(40,651)	(32,989)
Acquisition of net assets of Residential Control Systems, Inc.	(8,894)	0	0
Acquisition of intangible assets	(1,949)	(1,912)	(2,395)
Increase in restricted cash	0	(4,797)	0
Deposit received toward sale of Guangzhou factory	0	4,797	0
Deconsolidation of Encore Controls LLC	0	48	0
Acquisition of net assets of Ecolink Intelligent Technology, Inc., net of cash acquired	0	0	(12,265)
Net cash used for investing activities	(51,227)	(42,515)	(47,649)
Cash provided by (used for) financing activities:
Borrowings under line of credit	157,000	147,974	84,500
Repayments on line of credit	(68,987)	(147,987)	(34,500)
Proceeds from stock options exercised	1,442	6,244	1,712
Treasury stock purchased	(39,085)	(12,647)	(89,395)
Excess tax benefit from stock-based compensation	0	1,970	2,619
Distribution to noncontrolling interest	0	0	(78)
Net cash provided by (used for) financing activities	50,370	(4,446)	(35,142)
Effect of exchange rate changes on cash	(1,104)	(4,937)	(2,858)
Net increase (decrease) in cash and cash equivalents	11,827	(2,355)	(59,555)
Cash and cash equivalents at beginning of year	50,611	52,966	112,521
Cash and cash equivalents at end of period	62,438	50,611	52,966
Supplemental cash flow information:
Income taxes paid	8,280	9,891	7,793
Interest paid	$ 2,751	$ 1,208	$ 255