CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating activities
Net income	$ 43,354	$ 40,476
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	77,816	48,522
Gain on sales of property and equipment	(5,066)	(2,830)
Change in deferred income taxes	(2,207)	0
Stock-based compensation	12,621	13,580
Equity in net loss from unconsolidated joint ventures	16,343	15,415
Net income from affiliates	(5,527)	(4,907)
Changes in assets and liabilities, net of the effects of acquisitions in 2018:
Receivables	(154,996)	(207,908)
Costs and estimated earnings in excess of billings, net	0	14,726
Contract assets, net	355	0
Inventories	(4,283)	(6,814)
Contributions to unconsolidated construction joint ventures	(89,000)	(3,937)
Distributions from unconsolidated construction joint ventures	15,581	33,374
Other assets, net	30,728	10,523
Accounts payable	41,672	90,799
Accrued expenses and other current liabilities, net	37,352	23,595
Net cash provided by operating activities	14,743	64,614
Investing activities
Purchases of marketable securities	(9,952)	(79,708)
Maturities of marketable securities	60,000	90,000
Purchases of property and equipment ($15,040 and $13,537 related to CCJVs)	(86,131)	(56,808)
Proceeds from sales of property and equipment	9,480	5,107
Cash paid to purchase businesses, net of cash and restricted cash acquired	(55,030)	0
Other investing activities, net	320	2,321
Net cash used in investing activities	(81,313)	(39,088)
Financing activities
Proceeds from debt	143,250	0
Debt principal repayments	(42,149)	(3,750)
Cash dividends paid	(16,328)	(15,506)
Repurchases of common stock	(6,369)	(6,713)
Distributions to non-controlling partners, net	(10,128)	(3,500)
Other financing activities, net	441	133
Net cash provided by (used in) financing activities	68,717	(29,336)
Net increase (decrease) in cash, cash equivalents and restricted cash	2,147	(3,810)
Cash and cash equivalents at beginning of period	233,711	189,326
Cash, cash equivalents and restricted cash of $5,599 at end of period	235,858	185,516
Cash paid during the period for:
Interest	9,029	6,720
Income taxes	8,576	2,689
Other non-cash operating activities:
Performance guarantees	0	5,761
Non-cash investing and financing activities:
Common stock issued in acquisition	321,075	0
Common stock issued in conversion of 8% Convertible Notes	53,086	0
Premium on 8.0% Convertible Notes	30,702	0
Restricted stock units issued, net of forfeitures	13,537	11,184
Accrued cash dividends	6,097	5,181
Accrued equipment purchases	$ 4,783	$ 2,440