Original and Further Restatement of the Consolidated Financial Statements - Effects of Restatements on Condensed Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 25,117	[1]	$ 28,924	$ 32,874	$ 30,767
Restricted cash	19,270	[1]	23,761
Trade accounts receivable, less allowances of $8,841 and $9,111 at March 31, 2014 and December 31, 2013, respectively	73,447	[1]	70,811
Inventories	70,677	[1]	72,678
Deferred income taxes	40,007	[1]	39,999
Prepaid expenses and other current assets	31,050	[1]	28,933
Total current assets	259,568	[1]	265,106
Property, plant and equipment, net	52,656	[1]	54,372
Patents and other intangible assets, net	8,518	[1]	9,046
Goodwill	53,565	[1]	53,565
Deferred income taxes	22,816	[1]	22,394
Other long-term assets	6,850	[1]	7,492
Total assets	403,973	[1]	411,975
Current liabilities:
Trade accounts payable	14,022	[1]	20,674
Other current liabilities	43,700	[1]	49,676
Total current liabilities	57,722	[1]	70,350
Long-term debt	20,000	[1]	20,000
Deferred income taxes	13,201	[1]	13,026
Other long-term liabilities	12,487	[1]	12,736
Total liabilities	103,410	[1]	116,112
Contingencies (Note 16)		[1]
Shareholders' equity:
Common shares $0.10 par value; 50,000,000 shares authorized; 18,365,910 and 18,102,335 issued and outstanding as of March 31, 2014 and December 31, 2013, respectively	1,836	[1]	1,810
Additional paid-in capital	223,356	[1]	216,653
Retained earnings	71,389	[1]	73,897
Accumulated other comprehensive income	3,982	[1]	3,503
Total shareholders' equity	300,563	[1]	295,863
Total liabilities and shareholders' equity	403,973	[1]	411,975
Further Restatement [Member]
Current assets:
Cash and cash equivalents	25,117		28,924	32,874	30,767
Restricted cash	19,270		23,761
Trade accounts receivable, less allowances of $8,841 and $9,111 at March 31, 2014 and December 31, 2013, respectively	73,447		70,811
Inventories	70,677		72,678
Deferred income taxes	40,007		39,999
Prepaid expenses and other current assets	31,050		28,933
Total current assets	259,568		265,106
Property, plant and equipment, net	52,656		54,372
Patents and other intangible assets, net	8,518		9,046
Goodwill	53,565		53,565
Deferred income taxes	22,816		22,394
Other long-term assets	6,850		7,492
Total assets	403,973		411,975
Current liabilities:
Trade accounts payable	14,022		20,674
Other current liabilities	43,700		49,676
Total current liabilities	57,722		70,350
Long-term debt	20,000		20,000
Deferred income taxes	13,201		13,026
Other long-term liabilities	12,487		12,736
Total liabilities	103,410		116,112
Contingencies (Note 16)
Shareholders' equity:
Common shares $0.10 par value; 50,000,000 shares authorized; 18,365,910 and 18,102,335 issued and outstanding as of March 31, 2014 and December 31, 2013, respectively	1,836		1,810
Additional paid-in capital	223,356		216,653
Retained earnings	71,389		73,897
Accumulated other comprehensive income	3,982		3,503
Total shareholders' equity	300,563		295,863
Total liabilities and shareholders' equity	403,973		411,975
Originally Reported [Member] | Further Restatement [Member]
Current assets:
Cash and cash equivalents	26,747		30,486	33,675	31,055
Restricted cash	19,270		23,761
Trade accounts receivable, less allowances of $8,841 and $9,111 at March 31, 2014 and December 31, 2013, respectively	76,917		75,567
Inventories	92,753		90,577
Deferred income taxes	33,956		33,947
Prepaid expenses and other current assets	28,781		25,906
Total current assets	278,424		280,244
Property, plant and equipment, net	52,532		54,606
Patents and other intangible assets, net	8,518		9,046
Goodwill	53,565		53,565
Deferred income taxes	18,758		18,336
Other long-term assets	6,743		7,385
Total assets	418,540		423,182
Current liabilities:
Trade accounts payable	14,022		20,674
Other current liabilities	41,467		46,146
Total current liabilities	55,489		66,820
Long-term debt	20,000		20,000
Deferred income taxes	13,307		13,132
Other long-term liabilities	12,487		12,736
Total liabilities	101,283		112,688
Contingencies (Note 16)
Shareholders' equity:
Common shares $0.10 par value; 50,000,000 shares authorized; 18,365,910 and 18,102,335 issued and outstanding as of March 31, 2014 and December 31, 2013, respectively	1,836		1,810
Additional paid-in capital	223,630		216,653
Retained earnings	88,550		89,332
Accumulated other comprehensive income	3,241		2,699
Total shareholders' equity	317,257		310,494
Total liabilities and shareholders' equity	418,540		423,182
Further Restatement Adjustments [Member] | Further Restatement [Member]
Current assets:
Cash and cash equivalents	(1,630)		(1,562)	(801)	(288)
Restricted cash
Trade accounts receivable, less allowances of $8,841 and $9,111 at March 31, 2014 and December 31, 2013, respectively	(3,470)		(4,756)
Inventories	(22,076)		(17,899)
Deferred income taxes	6,051		6,052
Prepaid expenses and other current assets	2,269		3,027
Total current assets	(18,856)		(15,138)
Property, plant and equipment, net	124		(234)
Patents and other intangible assets, net
Goodwill
Deferred income taxes	4,058		4,058
Other long-term assets	107		107
Total assets	(14,567)		(11,207)
Current liabilities:
Trade accounts payable
Other current liabilities	2,233		3,530
Total current liabilities	2,233		3,530
Long-term debt
Deferred income taxes	(106)		(106)
Other long-term liabilities
Total liabilities	2,127		3,424
Contingencies (Note 16)
Shareholders' equity:
Common shares $0.10 par value; 50,000,000 shares authorized; 18,365,910 and 18,102,335 issued and outstanding as of March 31, 2014 and December 31, 2013, respectively
Additional paid-in capital	(274)
Retained earnings	(17,161)		(15,435)
Accumulated other comprehensive income	741		804
Total shareholders' equity	(16,694)		(14,631)
Total liabilities and shareholders' equity	$ (14,567)		$ (11,207)

[1] Unaudited