CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Operating activities
Net loss	$ (15,743)	$ (7,579)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation, depletion and amortization	43,547	31,148
Gain on sales of property and equipment	(2,048)	(1,077)
Stock-based compensation	10,193	11,224
Equity in net loss from unconsolidated joint ventures	13,418	8,249
Net income from affiliates	(3,758)	(2,175)
Changes in assets and liabilities, net of the effects of acquisitions in 2018:
Receivables	(24,821)	(64,864)
Costs and estimated earnings in excess of billings, net	0	(28,284)
Contract assets, net	(76,166)	0
Inventories	(9,526)	(10,250)
Contributions to unconsolidated construction joint ventures	(55,733)	(750)
Distributions from unconsolidated construction joint ventures	11,201	32,494
Other assets, net	4,192	(7,037)
Accounts payable	24,559	52,417
Accrued expenses and other current liabilities, net	5,240	9,170
Net cash (used in) provided by operating activities	(75,445)	22,686
Investing activities
Purchases of marketable securities	(9,952)	(49,816)
Maturities of marketable securities	60,000	70,000
Purchases of property and equipment ($11,369 and $7,492 related to CCJVs)	(36,471)	(37,518)
Proceeds from sales of property and equipment	2,704	2,585
Cash paid to purchase businesses, net of cash and restricted cash acquired	(55,030)	0
Other investing activities, net	269	23
Net cash used in investing activities	(38,480)	(14,726)
Financing activities
Proceeds from long term debt	105,250	0
Long-term debt principal repayments	(1,250)	(2,500)
Cash dividends paid	(10,389)	(10,327)
Repurchases of common stock	(6,165)	(6,568)
Distributions to non-controlling partners	(6,400)	0
Other financing activities, net	429	177
Net cash provided by (used in) financing activities	81,475	(19,218)
Net decrease in cash, cash equivalents and restricted cash	(32,450)	(11,258)
Cash and cash equivalents at beginning of period	233,711	189,326
Cash, cash equivalents and restricted cash of $5,746 at end of period	201,261	178,068
Cash paid during the period for:
Interest	6,134	5,957
Income taxes	7,246	2,554
Other non-cash operating activities:
Performance guarantees	0	5,761
Non-cash investing and financing activities:
Common stock issued in acquisition	321,075	0
Premium on 8.0% Convertible Notes	30,702	0
Restricted stock units issued, net of forfeitures	13,022	11,254
Accrued cash dividends	$ 5,940	$ 5,179