Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income (loss)		$ 134,035	$ (79,703)	$ 115,549
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization		164,915	169,662	154,452
Goodwill and intangible asset impairment		0	78,625	0
Non-cash interest expense, net		2,994	2,633	7,355
Non-cash stock-based compensation expense		15,072	12,395	15,950
Excess tax benefit from stock-based compensation	[1]	(135)	(57)	(3,728)
Provision for deferred income taxes		(3,935)	3,925	13,756
Other non-cash items		4,835	1,537	5,955
Losses (gains), net, on asset sales, including fixed assets held-for-sale and discontinued operations		1,957	(8,191)	(6,434)
Changes in assets and liabilities, net of acquisitions:
Accounts receivable		(246,419)	362,275	163,773
Inventories		(22,232)	22,356	(12,621)
Other assets, current and long-term portion		41,093	(7,647)	(14,221)
Accounts payable and accrued expenses		66,078	(162,441)	(87,494)
Billings in excess of costs and earnings		12,131	(5,085)	(34,320)
Book overdrafts		4,069	4,699	9,911
Other liabilities, current and long-term portion		31,135	(27,570)	(4,872)
Net cash provided by operating activities		205,593	367,413	323,011
Cash flows used in investing activities:
Cash paid for acquisitions, net of cash acquired		(4,102)	(148)	(345,543)
Capital expenditures		(117,114)	(84,410)	(109,254)
Proceeds from sale of property and equipment		11,239	13,932	16,655
Payments for other investments		(32,169)	(127,480)	(4,092)
Proceeds from other investments		1,125	69,406	2,972
Net cash used in investing activities		(141,021)	(128,700)	(439,262)
Cash flows (used in) provided by financing activities:
Proceeds from credit facilities		1,681,424	1,702,431	2,385,971
Repayments of credit facilities		(1,627,129)	(1,742,077)	(1,939,612)
Repayment of senior convertible notes		0	0	(202,325)
Repayments of other borrowings		(10,694)	(13,843)	(15,700)
Payments of capital lease obligations		(57,980)	(57,095)	(51,587)
Repurchase of common stock		0	(100,000)	0
Proceeds from stock-based awards, net		4,200	1,566	1,113
Excess tax benefit from stock-based compensation		135	57	3,728
Payments of acquisition-related contingent consideration		(19,822)	(47,523)	(60,341)
Other financing activities, net		380	(2,436)	(2,572)
Net cash (used in) provided by financing activities		(29,486)	(258,920)	118,675
Effect of currency translation on cash		(1,303)	1,132	(1,292)
Net increase (decrease) in cash and cash equivalents		33,783	(19,075)	1,132
Cash and cash equivalents - beginning of period		4,984	24,059	22,927
Cash and cash equivalents - end of period		38,767	4,984	24,059
Supplemental cash flow information:
Interest paid		47,698	47,405	42,979
Income taxes paid, net of refunds		59,342	2,536	76,975
Supplemental disclosure of non-cash information:
Equipment acquired under capital lease		25,092	18,032	64,618
Accrued capital expenditures		1,582	3,164	4,818
Premium shares, conversion of convertible notes		0	0	155,744
Equipment [Member]
Supplemental disclosure of non-cash information:
Equipment acquired under financing arrangements		$ 0	$ 5,785	$ 6,287

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