Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Cash flows from operating activities:
Net income	$ 141,216		$ 107,416		$ 105,972
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	140,928		92,601		75,228
Non-cash interest expense, including write-off of deferred financing costs on redeemed debt	10,717		8,595		7,552
Non-cash stock-based compensation expense	12,944		4,433		3,573
Excess tax benefit from stock-based compensation	(4,315)	[1]	(759)	[1]	(7,766)	[1]
Provision for deferred income taxes	6,533		5,127		40,280
(Gains) losses on sales of assets	(7,528)		(1,208)		497
Loss on disposal and impairment charges, discontinued operations	6,036		12,922		0
Gain on remeasurement of equity interest in acquiree	0		0		(29,041)
Changes in assets and liabilities, net of non-cash transactions:
Accounts receivable	(204,330)		(177,313)		(180,839)
Inventories	13,481		15,448		(30,527)
Other assets, current and non-current portion	6,246		(7,416)		(26,957)
Accounts payable and accrued expenses	72,514		76,285		73,099
Billings in excess of costs and earnings	(8,227)		15,651		(34,712)
Book overdrafts	6,363		116		14,906
Other liabilities, current and non-current portion	(7,517)		20,954		(6,143)
Net cash provided by operating activities	200,402		172,508		20,732
Cash flows (used in) provided by investing activities:
Cash paid for acquisitions, net of cash acquired	(148,567)		(119,459)		(40,681)
Proceeds from disposal of business, net of cash divested	(2,997)		97,728		0
Capital expenditures	(126,288)		(79,686)		(71,710)
Proceeds from sale of property and equipment	15,858		7,385		6,227
Proceeds from sale or redemption of investments	14,956		0		4,600
Payments for other investments, net	(16,173)		(284)		(284)
Net cash used in investing activities	(263,211)		(94,316)		(101,848)
Cash flows provided by (used in) financing activities:
Proceeds from credit facility	1,149,040		959,183		370,411
Repayments of credit facility	(1,249,601)		(885,183)		(310,411)
Proceeds from issuance of 4.875% Senior Notes	400,000		0		0
Repayment of 7.625% Senior Notes	(150,000)		0		0
Repayments of other borrowings	(27,705)		(21,455)		(13,956)
Payments of capital lease obligations	(43,040)		(21,060)		(16,458)
Repurchase of common stock	0		(75,000)		(75,000)
Proceeds from stock stock-based awards, net of tax witholdings	8,355		5,013		12,542
Excess tax benefit from stock-based compensation	4,315		759		7,766
Payments of financing costs, including call premiums on extinguishment of debt	(13,688)		(117)		(6,589)
Net cash provided by (used in) financing activities	58,993		(71,796)		(76,409)
Net (decrease) increase in cash and cash equivalents	(3,816)		6,396		(157,525)
Net effect of currency translation on cash	(24)		91		201
Cash and cash equivalents - beginning of period	26,767		20,280		177,604
Cash and cash equivalents - end of period	22,927		26,767		20,280
Cash and cash equivalents of discontinued operations	0		385		12,874
Cash and cash equivalents of continuing operations	22,927		26,382		7,406
Supplemental cash flow information:
Interest paid	37,531		27,074		27,607
Income taxes paid, net of refunds	79,504		58,968		27,803
Supplemental disclosure of non-cash information:
Equipment acquired under capital lease	86,330		60,648		7,412
Unsecured Debt [Member] | 2011 Senior Convertible Notes [Member] | Convertible Debt [Member]
Supplemental disclosure of non-cash information:
Exchange of senior convertible notes	0		0		202,322
Contributed Shares [Member] | Investor [Member]
Supplemental disclosure of non-cash information:
Value of shares contributed by shareholder, former owner of acquired business	6,002		0		0
Machinery and Equipment [Member]
Supplemental disclosure of non-cash information:
Equipment acquired under financing arrangements	24,244		6,009		25,788
Equity Issued in Business Combination [Member]
Supplemental disclosure of non-cash information:
Shares issued in connection with business combinations	0		0		94,213
Machinery and Equipment [Member] | Lease Agreements [Member]
Supplemental disclosure of non-cash information:
Conversion of equipment leases from operating to capital	0		0		23,366
Inventories [Member]
Supplemental cash flow information:
Receipt of inventory prepaid in prior year	0		12,005		0
Earn-out Arrangements [Member]
Cash flows provided by (used in) financing activities:
Payments of acquisition-related contingent consideration	(18,683)		(33,936)		(44,714)
Supplemental disclosure of non-cash information:
Estimated fair value of contingent consideration	29,971		66,700		48,111
Operating Expense [Member]
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for losses on operating assets	8,009		9,305		5,101
Contracts Accounted for under Percentage of Completion [Member]
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for losses on construction projects, net	$ 7,332		$ (9,649)		$ 10,509

[1] Excess tax benefits, which represent cash flows from tax deductions in excess of the tax effect of compensation expense recognized for stock options exercised and vested restricted shares, are classified as financing cash flows in the Company’s consolidated statements of cash flows.