Consolidated Statements of Cash Flows - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Cash flows from operating activities:
Net income		$ 75,765	$ 56,827	$ 141,877	$ 92,889
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation		87,501	57,687	166,766	110,776
Amortization of intangible assets		19,923	9,793	31,170	17,184
Non-cash interest expense, net				1,563	1,451
Non-cash stock-based compensation expense				11,600	9,899
Benefit from deferred income taxes				(1,594)	(20,575)
Equity in earnings of unconsolidated affiliates		(7,525)	(6,813)	(14,871)	(14,647)
Gains on sales of assets, net				(5,975)	(8,334)
Other non-cash items, net				(7,836)	12,297
Changes in assets and liabilities, net of acquisitions:
Accounts receivable				32,710	(60,246)
Contract assets				(46,148)	64,321
Inventories				5,167	(4,629)
Other assets, current and long-term portion				(2,604)	31,234
Accounts payable and accrued expenses				60,452	164,297
Contract liabilities				(16,020)	130,784
Other liabilities, current and long-term portion				(6,915)	(59,481)
Net cash provided by operating activities				349,342	467,220
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired				(589,055)	(10,493)
Capital expenditures				(97,029)	(132,755)
Proceeds from sale of property and equipment				12,960	17,861
Payments for other investments				(6,197)	(16,777)
Proceeds from other investments				557	648
Other investing activities, net				2,650	4,843
Net cash used in investing activities				(676,114)	(136,673)
Cash flows from financing activities:
Proceeds from credit facilities				414,741	1,235,935
Repayments of credit facilities				(161,375)	(1,401,899)
Payments of finance lease obligations				(76,630)	(61,587)
Payments of acquisition-related contingent consideration				(20,893)	(10,097)
Payments to non-controlling interests, including acquisition of interests and distributions	$ 6,800			(8,888)	0
Payments for stock-based awards				(3,774)	(593)
Proceeds from stock-based awards				0	3,936
Repurchases of common stock				0	(120,228)
Other financing activities, net				(2,343)	(17)
Net cash provided by (used in) financing activities				140,838	(354,550)
Effect of currency translation on cash				87	1,214
Net decrease in cash and cash equivalents				(185,847)	(22,789)
Cash and cash equivalents - beginning of period				423,118	71,427	$ 71,427
Cash and cash equivalents - end of period	$ 237,271	$ 237,271	$ 48,638	237,271	48,638	$ 423,118
Supplemental cash flow information:
Interest paid				28,401	33,046
Income tax payments, net of refunds				61,180	1,469
Supplemental disclosure of non-cash information:
Additions to property and equipment from finance leases				$ 98,984	$ 44,987