CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash flows from operating activities:
Net income	$ 63,692	$ 54,477	$ 20,896
Adjustments to reconcile net income to net cash provided by operating activities:
Extinguishment of debt			13,985
Loss (gain) on interest rate swap and disposal of auction rate securities			1,798
Loss on disposals of assets	64	7	828
Reduction of seller notes and earnouts	(993)	(541)
Provision for doubtful accounts	19,773	24,837	20,276
Provision (benefit) for deferred income taxes	(4,303)	8,439	752
Depreciation and amortization	34,652	30,969	18,809
Amortization of debt issuance costs	3,452	3,334	1,893
Compensation expense on stock options and restricted stock	8,061	8,088	9,596
Changes in operating assets and liabilities, net of effects of acquired companies:
Accounts receivable	(40,443)	(42,024)	(31,041)
Inventories	(12,827)	(14,072)	(4,522)
Prepaid expenses, other current assets, and income taxes	3,867	796	(9,590)
Accounts payable	(2,114)	(5,902)	(190)
Accrued expenses, accrued interest payable	3,501	(1,424)	5,299
Accrued compensation related costs	4,348	(7,404)	5,599
Other	589	2,224	(188)
Net cash provided by operating activities	81,319	61,804	54,200
Cash flows from investing activities:
Purchase of property, plant and equipment (net of acquisitions)	(29,492)	(25,300)	(30,593)
Purchase of equipment leased to third parties under operating leases	(3,671)	(3,374)
Acquisitions and contingent considerations (net of cash acquired)	(62,500)	(14,842)	(162,250)
Restricted cash	(3,120)
Proceeds from sale of marketable securities			6,495
Purchase of company-owned life insurance investment	(2,000)	(4,000)
Proceeds from sale of property, plant and equipment	1,732	646	373
Net cash used in investing activities	(99,051)	(46,870)	(185,975)
Cash flows from financing activities:
Borrowings under revolving credit agreement		10,000
Repayments under revolving credit agreement		(10,000)
Repayment of term loan	(3,700)	(3,000)	(221,956)
Scheduled repayment of seller's notes	(5,255)	(4,151)	(3,810)
Repayment of capital lease obligations	(713)
Repayment of senior notes due 2014			(184,831)
Proceeds on senior notes due 2018			200,000
Proceeds on term loan			300,000
Deferred financing costs		(4,230)	(16,976)
Repayment of line of credit			(3,628)
Excess tax benefit from stock-based compensation	1,505	2,462	2,342
Proceeds from issuance of common stock	3,560	2,680	12,384
Purchase and retirement of common stock	(1,350)	(2,107)
Net cash (used in) provided by financing activities	(5,953)	(8,346)	83,525
Increase (decrease) in cash and cash equivalents	(23,685)	6,588	(48,250)
Cash and cash equivalents, at beginning of year	42,896	36,308	84,558
Cash and cash equivalents, at end of year	$ 19,211	$ 42,896	$ 36,308