Condensed Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net income	$ 106,864	$ 123,959
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	101,615	88,282
Non-cash interest expense, net	1,451	1,615
Non-cash stock-based compensation expense	6,571	7,166
(Benefit from) provision for deferred income taxes	(172)	76,584
Equity in earnings of unconsolidated affiliates	(11,409)	(7,706)
Gains on sales of assets, net, including fixed assets held-for-sale	(6,920)	(1,873)
Other non-cash items, net	2,686	13,190
Changes in assets and liabilities, net of acquisitions:
Accounts receivable, net	(471,716)	(388,818)
Inventories	(8,550)	28,295
Other assets, current and long-term portion	58,949	(81,286)
Accounts payable and accrued expenses	180,150	113,975
Billings in excess of costs and earnings	44,524	(58,594)
Book overdrafts	8,361	(9,760)
Other liabilities, current and long-term portion	10,813	(5,189)
Net cash provided by (used in) operating activities	23,217	(100,160)
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	(6,684)	(37,444)
Capital expenditures	(87,997)	(56,853)
Proceeds from sale of property and equipment	13,884	7,369
Payments for other investments	(35,713)	(74,482)
Proceeds from other investments	5,415	12,118
Net cash used in investing activities	(111,095)	(149,292)
Cash flows from financing activities:
Proceeds from credit facilities	1,638,874	1,153,230
Repayments of credit facilities	(1,374,552)	(869,100)
Repayments of other borrowings	(15,800)	(10,291)
Payments of capital lease obligations	(37,926)	(30,858)
Payments of acquisition-related contingent consideration	(15,929)	(6,676)
Repurchase of common stock	(128,311)	0
Distributions to non-controlling interests	(559)	(1,280)
Proceeds from stock-based awards, net	1,927	5
Other financing activities	0	(6,240)
Net cash provided by financing activities	67,724	228,790
Effect of currency translation on cash	512	125
Net decrease in cash and cash equivalents	(19,642)	(20,537)
Cash and cash equivalents - beginning of period	40,326	38,767
Cash and cash equivalents - end of period	20,684	18,230
Supplemental cash flow information:
Interest paid	36,068	25,743
Income tax (refunds) payments, net	(13,975)	76,633
Supplemental disclosure of non-cash information:
Additions to acquisition-related contingent consideration	3,510	25,000
Equipment acquired under capital lease and financing arrangements	39,548	109,914
Accrued capital expenditures	$ 12,315	$ 1,499