Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income (loss)	$ 348,884	$ 134,035	$ (79,703)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	188,049	164,915	169,662
Goodwill and intangible asset impairment	0	0	78,625
Non-cash interest expense, net	3,100	2,994	2,633
Non-cash stock-based compensation expense	15,656	15,072	12,395
Provision for (benefit from) deferred income taxes	18,277	(3,935)	3,925
Equity in (earnings) losses of unconsolidated affiliates	(21,328)	(3,528)	7,978
(Gains) losses on sales of assets, net, including fixed assets held-for-sale	(5,935)	1,957	(8,191)
Other non-cash items, net	7,222	4,700	1,480
Changes in assets and liabilities, net of acquisitions:
Accounts receivable	(417,491)	(246,419)	362,275
Inventories	36,187	(22,232)	22,356
Other assets, current and long-term portion	(117,091)	44,650	(11,241)
Accounts payable and accrued expenses	54,342	66,078	(162,441)
Billings in excess of costs and earnings	46,075	12,131	(5,085)
Book overdrafts	(10,459)	4,069	4,699
Other liabilities, current and long-term portion	10,775	31,106	(31,954)
Net cash provided by operating activities	156,263	205,593	367,413
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	(115,995)	(4,102)	(148)
Capital expenditures	(123,412)	(117,114)	(84,410)
Proceeds from sale of property and equipment	19,963	11,239	13,932
Payments for other investments	(77,105)	(32,169)	(127,480)
Proceeds from other investments	23,801	1,125	69,406
Net cash used in investing activities	(272,748)	(141,021)	(128,700)
Cash flows from financing activities:
Proceeds from credit facilities	2,699,047	1,681,424	1,702,431
Repayments of credit facilities	(2,457,293)	(1,627,129)	(1,742,077)
Repayments of other borrowings, net	(3,350)	(10,694)	(13,843)
Payments of capital lease obligations	(67,740)	(57,980)	(57,095)
Payments of acquisition-related contingent consideration	(18,843)	(19,822)	(47,523)
Payments to non-controlling interests, including acquisition of interests and distributions	(22,728)	0	0
(Payments for) proceeds from stock-based awards, net	(3,085)	4,200	1,566
Repurchase of common stock	(1,552)	0	(100,000)
Other financing activities, net	(6,301)	515	(2,379)
Net cash provided by (used in) financing activities	118,155	(29,486)	(258,920)
Effect of currency translation on cash	(111)	(1,303)	1,132
Net increase (decrease) in cash and cash equivalents	1,559	33,783	(19,075)
Cash and cash equivalents - beginning of period	38,767	4,984	24,059
Cash and cash equivalents - end of period	40,326	38,767	4,984
Supplemental cash flow information:
Interest paid	59,157	47,698	47,405
Income taxes paid, net of refunds	78,653	59,342	2,536
Supplemental disclosure of non-cash information:
Equipment acquired under capital lease and financing arrangements	150,055	25,092	23,817
Accrued capital expenditures	4,716	1,582	3,164
Earn-Out Liabilities [Member]
Supplemental disclosure of non-cash information:
Additions to acquisition-related contingent consideration	$ 102,534	$ 0	$ 0