RESTATEMENT OF PREVIOUSLY ISSUED CONSOLIDATED FINANCIAL STATEMENTS - BALANCE SHEET (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Current assets:
Cash and cash equivalents	$ 11,699	$ 1,565	$ 1,630	$ 45,836	$ 1,613	$ 1,246	$ 2,858	$ 6,273	$ 13,130	$ 13,130	$ 43,323
Accounts receivable, net of allowance for doubtful accounts of $6,472	174,248	165,787	159,471	146,060	154,739	149,952	150,276	139,756
Accounts receivable, allowance for doubtful accounts (in dollars)	9,944	10,197	9,078	7,920	6,472	5,837	4,971	4,941	4,928		3,844
Inventories	70,517	86,155	90,506	85,783	82,257	83,293	81,214	79,575
Other current assets	21,356	46,604	33,097	27,466	21,606	22,861	28,937	29,313
Deferred income taxes	109,252	70,333	70,789	71,569	75,616	64,209	64,153	61,055
Total current assets	395,287	370,444	355,493	376,714	335,831	321,561	327,438	315,972
Non-current assets:
Property, plant and equipment, net	112,350	114,223	119,677	120,225	116,289	113,144	109,475	106,249
Goodwill	710,053	716,571	715,010	702,769	682,628	679,721	678,748	675,451	675,468
Other intangible assets, net	58,515	60,553	62,600	60,352	56,240	56,906	58,520	59,311
Debt issuance costs, net	6,648	7,110	7,572	8,034	8,496	8,958	9,420	13,169
Other assets	19,452	20,055	18,384	17,826	15,504	16,305	15,872	16,064
Total assets	1,302,305	1,288,956	1,278,736	1,285,920	1,214,988	1,196,595	1,199,473	1,186,216	1,201,288
Current liabilities:
Current portion of long-term debt	26,852	25,677	24,505	21,906	17,728	15,437	15,652	13,229
Accounts payable	48,554	49,658	45,642	43,964	44,519	44,921	47,798	36,189
Accrued expenses and other current liabilities	91,778	68,118	47,436	44,508	44,433	41,043	41,605	40,096
Accrued interest payable	2,366	5,950	2,274	5,646	2,019	5,934	2,351	6,645
Accrued compensation related costs	41,288	35,656	24,664	21,417	38,606	35,304	25,914	22,084
Total current liabilities	210,838	185,059	144,521	137,441	147,305	142,639	133,320	118,243
Long-term liabilities:
Long-term debt, less current portion	502,132	511,698	535,093	559,096	469,818	474,068	505,751	522,189
Deferred income taxes	59,924	62,786	62,338	61,640	65,329	65,906	65,935	66,489
Other liabilities	45,875	44,150	44,734	42,120	41,223	39,256	37,744	37,257
Total liabilities	818,769	803,693	786,686	800,297	723,675	721,869	742,750	744,178
Commitments and contingent liabilities
Shareholders' Equity:
Common stock, $.01 par value; 60,000,000 shares authorized, 35,158,196 shares issued and 35,017,042 shares outstanding	$ 355	$ 355	$ 355	$ 355	$ 351	$ 352	$ 352	$ 350
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01
Common stock, shares authorized	60,000,000	60,000,000	60,000,000	60,000,000	60,000,000	60,000,000	60,000,000	60,000,000
Common stock, shares issued	35,540,630	35,537,528	35,527,002	35,486,033	35,158,196	35,062,367	35,062,931	34,953,812
Common stock, shares outstanding	35,399,476	35,396,374	35,385,848	35,344,879	35,017,042	34,921,213	34,921,777	34,812,658
Additional paid-in capital	$ 307,166	$ 304,596	$ 302,581	$ 299,384	$ 295,113	$ 291,455	$ 288,971	$ 285,486
Accumulated other comprehensive loss	(1,888)	(1,020)	(1,020)	(1,020)	(1,020)	(1,919)	(1,919)	(1,919)
Retained earnings	178,559	181,988	190,790	187,560	197,525	185,494	169,975	158,777	157,014		108,990
Shareholders' equity, excluding treasury stock	484,192	485,919	492,706	486,279	491,969	475,382	457,379	442,694
Treasury stock at cost, 141,154 shares	$ (656)	$ (656)	$ (656)	$ (656)	$ (656)	$ (656)	$ (656)	$ (656)
Treasury stock, shares	141,154	141,154	141,154	141,154	141,154	141,154	141,154	141,154
Total shareholders' equity	$ 483,536	$ 485,263	$ 492,050	$ 485,623	$ 491,313	$ 474,726	$ 456,723	$ 442,038	437,055		378,031
Total liabilities and shareholders' equity	$ 1,302,305	$ 1,288,956	1,278,736	1,285,920	1,214,988	1,196,595	1,199,473	1,186,216
As Previously Reported
Current assets:
Cash and cash equivalents			4,902	55,624	9,860	7,216	5,766	15,033	19,211		42,896
Accounts receivable, net of allowance for doubtful accounts of $6,472			205,325	183,548	185,769	176,663	170,601	156,813
Inventories			158,957	153,952	141,518	144,374	137,557	132,492
Other current assets			21,147	27,678	15,519	14,560	21,453	22,911
Deferred income taxes			30,381	30,366	30,298	31,115	30,920	28,043
Total current assets			420,712	451,168	382,964	373,928	366,297	355,292
Non-current assets:
Property, plant and equipment, net			142,650	131,419	126,798	115,963	115,242	111,901
Goodwill			715,656	702,455	681,547	678,215	676,190	674,416
Other intangible assets, net			62,517	61,367	58,021	58,638	61,262	62,661
Debt issuance costs, net			7,703	8,134	8,564	8,994	9,424	13,169
Other assets			15,321	15,142	13,766	12,261	11,209	11,482
Total assets			1,364,559	1,369,685	1,271,660	1,247,999	1,239,624	1,228,921
Current liabilities:
Current portion of long-term debt			23,638	20,869	15,998	13,673	13,802	11,528
Accounts payable			31,815	41,789	36,729	32,339	34,314	26,345
Accrued expenses and other current liabilities			26,339	22,734	24,923	30,391	24,496	23,089
Accrued interest payable			2,049	5,534	1,898	5,772	2,205	6,516
Accrued compensation related costs			23,051	21,605	36,331	33,991	24,940	22,134
Total current liabilities			106,892	112,531	115,879	116,166	99,757	89,612
Long-term liabilities:
Long-term debt, less current portion			516,251	541,066	452,261	457,384	490,672	506,958
Deferred income taxes			76,784	76,971	76,545	76,480	76,509	77,730
Other liabilities			58,589	48,615	46,755	40,869	39,638	38,989
Total liabilities			758,516	779,183	691,440	690,899	706,576	713,289
Commitments and contingent liabilities
Shareholders' Equity:
Common stock, $.01 par value; 60,000,000 shares authorized, 35,158,196 shares issued and 35,017,042 shares outstanding			364	363	361	360	360	359
Additional paid-in capital			299,927	297,006	292,722	288,860	286,467	283,130
Accumulated other comprehensive loss			(1,020)	(1,020)	(1,020)	(1,919)	(1,919)	(1,919)
Retained earnings			307,428	294,809	288,813	270,455	248,796	234,718	225,229		161,537
Shareholders' equity, excluding treasury stock			606,699	591,158	580,876	557,756	533,704	516,288
Treasury stock at cost, 141,154 shares			(656)	(656)	(656)	(656)	(656)	(656)
Total shareholders' equity			606,043	590,502	580,220	557,100	533,048	515,632				$ 428,582
Total liabilities and shareholders' equity			1,364,559	1,369,685	1,271,660	1,247,999	1,239,624	1,228,921
Restatement Adjustments
Current assets:
Cash and cash equivalents			(3,272)	(9,788)	(8,247)	(5,970)	(2,908)	(8,760)	$ (6,081)		$ 427
Accounts receivable, net of allowance for doubtful accounts of $6,472			(45,854)	(37,488)	(31,030)	(26,711)	(20,325)	(17,057)
Inventories			(68,451)	(68,169)	(59,261)	(61,081)	(56,343)	(52,917)
Other current assets			11,950	(212)	6,087	8,301	7,484	6,402
Deferred income taxes			40,408	41,203	45,318	33,094	33,233	33,012
Total current assets			(65,219)	(74,454)	(47,133)	(52,367)	(38,859)	(39,320)
Non-current assets:
Property, plant and equipment, net			(22,973)	(11,194)	(10,509)	(2,819)	(5,767)	(5,652)
Goodwill			(646)	314	1,081	1,506	2,558	1,035
Other intangible assets, net			83	(1,015)	(1,781)	(1,732)	(2,742)	(3,350)
Debt issuance costs, net			(131)	(100)	(68)	(36)	(4)
Other assets			3,063	2,684	1,738	4,044	4,663	4,582
Total assets			(85,823)	(83,765)	(56,672)	(51,404)	(40,151)	(42,705)
Current liabilities:
Current portion of long-term debt			867	1,037	1,730	1,764	1,850	1,701
Accounts payable			13,827	2,175	7,790	12,582	13,484	9,844
Accrued expenses and other current liabilities			21,097	21,774	19,510	10,652	17,109	17,007
Accrued interest payable			225	112	121	162	146	129
Accrued compensation related costs			1,613	(188)	2,275	1,313	974	(50)
Total current liabilities			37,629	24,910	31,426	26,473	33,563	28,631
Long-term liabilities:
Long-term debt, less current portion			18,842	18,030	17,557	16,684	15,079	15,231
Deferred income taxes			(14,446)	(15,331)	(11,216)	(10,574)	(10,574)	(11,241)
Other liabilities			(13,855)	(6,495)	(5,532)	(1,613)	(1,894)	(1,732)
Total liabilities			28,170	21,114	32,235	30,970	36,174	30,889
Commitments and contingent liabilities
Shareholders' Equity:
Common stock, $.01 par value; 60,000,000 shares authorized, 35,158,196 shares issued and 35,017,042 shares outstanding			(9)	(8)	(10)	(8)	(8)	(9)
Additional paid-in capital			2,654	2,378	2,391	2,595	2,504	2,356
Retained earnings			(116,638)	(107,249)	(91,288)	(84,961)	(78,821)	(75,941)
Shareholders' equity, excluding treasury stock			(113,993)	(104,879)	(88,907)	(82,374)	(76,325)	(73,594)
Total shareholders' equity			(113,993)	(104,879)	(88,907)	(82,374)	(76,325)	(73,594)
Total liabilities and shareholders' equity			$ (85,823)	$ (83,765)	$ (56,672)	$ (51,404)	$ (40,151)	$ (42,705)