QUARTERLY FINANCIAL INFORMATION - STATEMENTS OF CASH FLOWS (Details) - USD ($) $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2014	Jun. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net (loss) income	$ (3,429)	$ (8,801)	$ 3,231	$ (9,967)	$ 12,032	$ 15,518	$ 11,197	$ 1,764	$ (6,736)	$ 12,961	$ (15,537)	$ 28,479	$ (18,966)	$ 40,511	$ 48,024
(Loss) income from discontinued operations, net of income taxes	(6,235)	(10,751)	4,661	(3,621)	(3,063)	(2,034)	(282)	11	1,040	(271)	(9,711)	(2,305)	(15,946)	(5,368)	(235)
(Loss) income from continuing operations	2,806	1,950	(1,430)	(6,346)	15,095	17,552	11,479	1,753	(7,776)	13,232	(5,826)	30,784	(3,020)	45,879	48,259
Adjustments to reconcile net (loss) income to net cash (used in) provided by operating activities:
Depreciation and amortization	9,978	9,818	9,826	9,307	8,487	8,526	8,805	8,367	19,133	17,172	28,951	25,698	38,929	34,185	32,589
Provision for doubtful accounts				1,989				474	4,463	1,705	9,094	3,441	11,639	5,053	4,423
Impairment of long-lived assets and intangible assets											1,503		2,425
Compensation expense on restricted stock units				2,356				2,093	5,152	4,599	7,138	7,004	9,642	9,346	8,213
Provision (benefit) for deferred income taxes				358					1,836	(2,564)	2,535	(2,564)	(39,214)	(14,499)	(13,812)
Amortization of debt issuance costs				617				1,038	1,306	1,975	1,987	2,607	2,663	3,218	3,891
Loss on extinguishment of debt							6,645			6,645		6,645		6,645
(Gain) loss on sale of property, plant and equipment				(553)				(277)	(620)	(900)	(1,412)	(6,369)	(293)	(6,258)	(2,019)
Contingent consideration gains										(57)	(49)	(702)	(85)	(1,461)	(1,388)
Changes in operating assets and liabilities, net of effects of acquired companies:
Net accounts receivable				9,521				9,332	(5,076)	747	(16,599)	791	(28,797)	(8,855)	(15,534)
Inventories				(2,293)				(1,449)	(5,897)	(2,258)	(2,212)	(3,740)	6,917	(3,493)	322
Other current assets and income taxes				(3,966)				(2,845)	(8,560)	(953)	(21,566)	2,130	9,351	7,009	1,498
Accounts payable				(4,335)				(639)	(2,971)	11,141	(751)	5,940	(777)	5,096	1,264
Accrued expenses, other current liabilities and accrued interest payable				2,117				3,990	1,172	(269)	25,499	3,158	40,186	687	3,451
Accrued compensation related costs				(17,779)				(23,186)	(15,050)	(18,900)	(3,618)	(9,952)	(483)	(6,566)	2,807
Other liabilities				(144)				198	1,511	572	(750)	1,969	978	4,148	(169)
Net cash provided by operating activities - continuing operations				(9,151)				(1,151)	(11,377)	31,887	23,924	66,840	50,061	80,134	73,795
Net cash (used in) provided by operating activities - discontinued operations				(1,479)				109	3,482	(2,227)	(1,774)	(2,261)	(442)	(3,102)	(3,037)
Net cash provided by operating activities				(10,630)				(1,042)	(7,895)	29,660	22,150	64,579	49,619	77,032	70,758
Cash flows from investing activities:
Purchase of property, plant and equipment, net of acquisitions				(8,526)				(3,450)	(14,805)	(13,741)	(18,924)	(19,174)	(27,096)	(25,907)	(24,503)
Purchase of equipment leased to third parties under operating leases				(564)				(660)	(1,663)	(1,849)	(2,609)	(2,889)	(4,012)	(4,103)	(2,763)
Acquisitions, net of cash acquired				(19,142)				(65)	(33,934)	(5,776)	(36,784)	(6,621)	(38,097)	(10,295)	(61,401)
Change in restricted cash associated with workers' compensation program												3,120		3,120	(3,120)
Purchase of company-owned life insurance investment				(2,294)					(2,294)		(2,294)		(2,294)		(2,000)
Proceeds from sale of property, plant and equipment				595				663	1,674	1,644	2,331	4,717	2,518	9,066	3,231
Net cash used in investing activities - continuing operations				(29,931)				(3,512)	(51,022)	(19,722)	(58,280)	(20,847)	(68,981)	(28,119)	(90,556)
Net cash provided by (used in) investing activities - discontinued operations				(265)				(256)	(464)	(604)	(532)	(944)	2,507	(1,438)	(1,118)
Net cash used in investing activities				(30,196)				(3,768)	(51,486)	(20,326)	(58,812)	(21,791)	(66,474)	(29,557)	(91,674)
Cash flows from financing activities:
Borrowings under term loan										225,000		225,000		225,000
Repayment of term loan				(1,406)				(750)	(2,813)	(293,300)	(5,625)	(294,706)	(8,438)	(296,113)	(3,700)
Borrowings under revolving credit agreement				125,000				50,000	228,000	120,000	252,000	163,000	331,000	249,000
Repayments under revolving credit agreement				(38,000)				(50,000)	(163,000)	(65,000)	(203,000)	(137,000)	(286,000)	(224,000)
Payment of seller notes				(1,631)				(1,411)	(3,569)	(3,117)	(6,845)	(6,449)	(9,435)	(8,656)	(4,904)
Payment of contingent consideration				(375)				(675)	(626)	(925)	(700)	(1,965)	(825)	(2,590)	(2,915)
Payment of financing obligations				(426)				(324)	(866)	(658)	(1,491)	(997)	(1,687)	(1,367)	(1,104)
Payment of fees associated with debt modifications and extinguishments										(3,665)		(3,665)		(3,665)
Excess tax benefit from stock-based compensation				1,803				1,054	2,191	2,005	2,197	2,058	2,249	3,348	1,489
Proceeds from issuance of common stock				87				62	87	1,628	87	1,629	87	2,437	3,560
Purchase and retirement of common stock										(1,567)		(1,567)		(2,374)	(1,350)
Net cash provided by (used in) financing activities - continuing operations				85,052				(2,044)	59,404	(19,599)	36,623	(54,662)	26,951	(58,980)	(8,924)
Net cash used in financing activities - discontinued operations				(3)				(3)	(6)	(7)	(9)	(10)	(10)	(12)	(353)
Net cash provided by (used in) financing activities				85,049				(2,047)	59,398	(19,606)	36,614	(54,672)	26,941	(58,992)	(9,277)
Increase (decrease) in cash and cash equivalents				44,223				(6,857)	17	(10,272)	(48)	(11,884)	10,086	(11,517)	(30,193)
Cash and cash equivalents, at beginning of year	1,565	1,630	45,836	1,613	1,246	2,858	6,273	13,130	1,613	13,130	1,613	13,130	1,613	13,130	43,323
Cash and cash equivalents, at end of year	$ 11,699	1,565	1,630	45,836	1,613	1,246	2,858	6,273	1,630	2,858	1,565	1,246	11,699	1,613	13,130
Cash paid during the period for:
Interest				2,537				4,221	12,344	16,314	15,283	19,144	25,341	28,938	31,122
Income taxes (net of refunds)				11,159				5,591	11,538	15,558	19,095	21,033	25,433	34,409	34,468
Non-cash financing and investing activities:
Issuance of seller notes in connection with acquisitions				8,450					11,901	268	13,172	614	13,964	2,344	20,223
Additions to property, plant and equipment acquired through financing obligations				1,266				386	1,973	740	3,001	2,797	3,461	3,958	3,094
Retirements of financed property, plant and equipment				7					7	150	2,097	529	2,071	399	2,095
Purchase of property, plant and equipment in accounts payable				2,184				357	1,169	574	1,793	638	1,588	1,109	416
As Previously Reported
Cash flows from operating activities:
Net (loss) income			12,619	5,997	18,356	21,659	14,079	9,490	18,616	23,569		45,228		63,584	63,692
(Loss) income from continuing operations			12,619	5,997	18,356	21,659	14,079	9,490	18,616	23,569		45,228		63,584	63,692
Adjustments to reconcile net (loss) income to net cash (used in) provided by operating activities:
Depreciation and amortization			12,133	10,199	9,467	9,224	9,510	9,285	22,332	18,795		28,019		37,486	34,652
Provision for doubtful accounts				3,754				1,657	8,808	4,591		8,545		14,330	9,589
Compensation expense on restricted stock units				2,418				1,667	5,265	4,060		6,398		9,080	8,061
Provision (benefit) for deferred income taxes				358					358	(2,564)		(2,564)		(1,602)	(4,303)
Amortization of debt issuance costs				430				864	861	8,273		8,703		2,488	3,452
Loss on extinguishment of debt							6,645			6,645		6,645		6,645
(Gain) loss on sale of property, plant and equipment				(547)				52	(939)	169		(5,570)		(5,914)	64
Contingent consideration gains									(318)	(57)		(363)		(1,032)	(993)
Changes in operating assets and liabilities, net of effects of acquired companies:
Net accounts receivable				1,537				7,216	(23,564)	(7,712)		(14,586)		(32,060)	(30,259)
Inventories				(10,589)				(5,197)	(14,467)	(7,940)		(14,676)		(11,329)	(12,827)
Other current assets and income taxes				(12,736)				(3,860)	(5,104)	(2,746)		5,028		4,689	3,867
Accounts payable				2,126				(2,006)	(6,430)	7,611		4,581		6,235	(2,114)
Accrued expenses, other current liabilities and accrued interest payable				2,384				3,883	1,080	(202)		5,421		(223)	3,501
Accrued compensation related costs				(15,040)				(19,544)	(13,772)	(18,612)		(9,584)		(7,379)	4,348
Other liabilities				(253)				(1,314)	(211)	409		3,946		1,262	589
Net cash provided by operating activities - continuing operations				(9,962)				2,193	(7,485)	27,644		68,526		86,260	81,319
Net cash provided by operating activities				(9,962)				2,193	(7,485)	27,644		68,526		86,260	81,319
Cash flows from investing activities:
Purchase of property, plant and equipment, net of acquisitions				(8,297)				(5,110)	(20,248)	(15,939)		(24,429)		(34,236)	(29,492)
Purchase of equipment leased to third parties under operating leases				(564)				(288)	(1,438)	(2,106)		(3,041)		(4,210)	(3,671)
Acquisitions, net of cash acquired				(19,167)					(34,201)	(4,741)		(5,695)		(9,296)	(62,500)
Change in restricted cash associated with workers' compensation program												3,120		3,120	(3,120)
Purchase of company-owned life insurance investment				(2,294)					(2,294)						(2,000)
Proceeds from sale of property, plant and equipment				522				91	1,079	894		4,595		8,684	1,732
Net cash used in investing activities - continuing operations				(29,800)				(5,307)	(57,102)	(21,892)		(25,450)		(35,938)	(99,051)
Net cash used in investing activities				(29,800)				(5,307)	(57,102)	(21,892)		(25,450)		(35,938)	(99,051)
Cash flows from financing activities:
Borrowings under term loan										225,000		225,000		225,000
Repayment of term loan				(1,406)				(750)	(2,813)	(293,300)		(294,706)		(296,113)	(3,700)
Borrowings under revolving credit agreement				125,000					228,000	120,000		163,000		249,000
Repayments under revolving credit agreement				(38,000)					(163,000)	(65,000)		(137,000)		(224,000)
Payment of seller notes				(1,594)				(1,410)	(3,765)	(4,042)		(9,168)		(12,410)	(5,255)
Payment of financing obligations				(340)				(180)	(754)	(411)		(808)		(1,047)	(713)
Payment of fees associated with debt modifications and extinguishments										(3,665)		(3,665)		(3,667)
Excess tax benefit from stock-based compensation				1,780				1,214	1,875	2,159		2,214		3,501	1,505
Proceeds from issuance of common stock				86				62	86	1,628		1,628		2,437	3,560
Purchase and retirement of common stock										(1,566)		(1,566)		(2,374)	(1,350)
Net cash provided by (used in) financing activities - continuing operations				85,526				(1,064)	59,629	(19,197)		(55,071)		(59,673)	(5,953)
Net cash provided by (used in) financing activities				85,526				(1,064)	59,629	(19,197)		(55,071)		(59,673)	(5,953)
Increase (decrease) in cash and cash equivalents				45,764				(4,178)	(4,958)	(13,445)		(11,995)		(9,351)	(23,685)
Cash and cash equivalents, at beginning of year		4,902	55,624	9,860	7,216	5,766	15,033	19,211	9,860	19,211	9,860	19,211	9,860	19,211	42,896
Cash and cash equivalents, at end of year			4,902	55,624	9,860	7,216	5,766	15,033	4,902	5,766		7,216		9,860	19,211
Cash paid during the period for:
Interest				1,629				3,290	10,537	13,105		16,299
Income taxes (net of refunds)				11,159				5,591	11,538	14,973		21,033
Non-cash financing and investing activities:
Issuance of seller notes in connection with acquisitions				9,300					12,900	300		675
Additions to property, plant and equipment acquired through financing obligations									10,717	220
Restatement Adjustments
Cash flows from operating activities:
Net (loss) income				(15,964)				(7,726)	(25,352)	(10,608)		(16,749)		(23,073)	(15,668)
(Loss) income from discontinued operations, net of income taxes				(3,621)				11	1,040	(271)		(2,305)		(5,368)	(235)
(Loss) income from continuing operations				(12,343)				(7,737)	(26,392)	(10,337)		(14,444)		(17,705)	(15,433)
Adjustments to reconcile net (loss) income to net cash (used in) provided by operating activities:
Depreciation and amortization				(892)				(918)	(3,199)	(1,623)		(2,321)		(3,301)	(2,063)
Provision for doubtful accounts				(1,765)				(1,183)	(4,345)	(2,886)		(5,104)		(9,277)	(5,166)
Compensation expense on restricted stock units				(62)				426	(113)	539		606		266	152
Provision (benefit) for deferred income taxes									1,478					(12,897)	(9,509)
Amortization of debt issuance costs				187				174	445	(6,298)		(6,096)		730	439
Loss on extinguishment of debt										6,645		6,645
(Gain) loss on sale of property, plant and equipment				(6)				(329)	319	(1,069)		(799)		(344)	(2,083)
Contingent consideration gains									318			(339)		(429)	(395)
Changes in operating assets and liabilities, net of effects of acquired companies:
Net accounts receivable				7,984				2,116	18,488	8,459		15,377		23,205	14,725
Inventories				8,296				3,748	8,570	5,682		10,936		7,836	13,149
Other current assets and income taxes				8,770				1,015	(3,456)	1,793		(2,898)		2,320	(2,369)
Accounts payable				(6,461)				1,367	3,459	3,530		1,359		(1,139)	3,378
Accrued expenses, other current liabilities and accrued interest payable				(267)				107	92	(67)		(2,263)		910	(50)
Accrued compensation related costs				(2,739)				(3,642)	(1,278)	(288)		(368)		813	(1,541)
Other liabilities				109				1,512	1,722	163		(1,977)		2,886	(758)
Net cash provided by operating activities - continuing operations				811				(3,344)	(3,892)	4,243		(1,686)		(6,126)	(7,524)
Net cash (used in) provided by operating activities - discontinued operations				(1,479)				109	3,482	(2,227)		(2,261)		(3,102)	(3,037)
Net cash provided by operating activities				(668)				(3,235)	(410)	2,016		(3,947)		(9,228)	(10,561)
Cash flows from investing activities:
Purchase of property, plant and equipment, net of acquisitions				(229)				1,660	5,443	2,198		5,255		8,329	4,989
Purchase of equipment leased to third parties under operating leases								(372)	(225)	257		152		107	908
Acquisitions, net of cash acquired				25				(65)	267	(1,035)		(926)		(999)	1,099
Proceeds from sale of property, plant and equipment				73				572	595	750		122		382	1,499
Net cash used in investing activities - continuing operations				(131)				1,795	6,080	2,170		4,603		7,819	8,495
Net cash provided by (used in) investing activities - discontinued operations				(265)				(256)	(464)	(604)		(944)		(1,438)	(1,118)
Net cash used in investing activities				(396)				1,539	5,616	1,566		3,659		6,381	7,377
Cash flows from financing activities:
Borrowings under revolving credit agreement								50,000
Repayments under revolving credit agreement								(50,000)
Payment of seller notes				(37)				(1)	196	925		2,719		3,754	351
Payment of contingent consideration				(375)				(675)	(626)	(925)		(1,965)		(2,590)	(2,915)
Payment of financing obligations				(86)				(144)	(112)	(247)		(189)		(320)	(391)
Payment of fees associated with debt modifications and extinguishments														2
Excess tax benefit from stock-based compensation				23				(160)	316	(154)		(156)		(153)	(16)
Proceeds from issuance of common stock				1					1			1
Purchase and retirement of common stock										(1)		(1)
Net cash provided by (used in) financing activities - continuing operations				(474)				(980)	(225)	(402)		409		693	(2,971)
Net cash used in financing activities - discontinued operations				(3)				(3)	(6)	(7)		(10)		(12)	(353)
Net cash provided by (used in) financing activities				(477)				(983)	(231)	(409)		399		681	(3,324)
Increase (decrease) in cash and cash equivalents				(1,541)				(2,679)	4,975	3,173		111		(2,166)	(6,508)
Cash and cash equivalents, at beginning of year		$ (3,272)	(9,788)	(8,247)	(5,970)	(2,908)	(8,760)	(6,081)	(8,247)	(6,081)	$ (8,247)	(6,081)	$ (8,247)	(6,081)	427
Cash and cash equivalents, at end of year			$ (3,272)	(9,788)	$ (8,247)	$ (5,970)	$ (2,908)	(8,760)	(3,272)	(2,908)		(5,970)		$ (8,247)	$ (6,081)
Cash paid during the period for:
Interest				908				931	1,807	3,209		2,845
Income taxes (net of refunds)										585
Non-cash financing and investing activities:
Issuance of seller notes in connection with acquisitions				(850)					(999)	(32)		(61)
Additions to property, plant and equipment acquired through financing obligations				1,266				386	(8,744)	520		2,797
Retirements of financed property, plant and equipment				7					7	150		529
Purchase of property, plant and equipment in accounts payable				$ 2,184				$ 357	$ 1,169	$ 574		$ 638