CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Mar. 31, 2014	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	$ (9,967)	$ 1,764	$ (6,736)	$ 12,961	$ (15,537)	$ 28,479	$ (18,966)	$ 40,511	$ 48,024
Loss from discontinued operations, net of income taxes	(3,621)	11	1,040	(271)	(9,711)	(2,305)	(15,946)	(5,368)	(235)
(Loss) income from continuing operations	(6,346)	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 provided by operating activities:
Depreciation and amortization	9,307	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
Benefit from 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
Gain 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 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	1,613	13,130	1,613	13,130	1,613	13,130	1,613	13,130	43,323
Cash and cash equivalents, at end of year	$ 45,836	$ 6,273	$ 1,630	$ 2,858	$ 1,565	$ 1,246	$ 11,699	$ 1,613	$ 13,130