Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating activities
Net (loss) income	$ (166,181)	$ (56,702)	$ 11,536
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation, depletion and amortization	112,958	121,993	111,544
Amortization related to the 2.75% Convertible Notes (See Note 14)	8,693	1,425	0
Gain on sales of property and equipment, net	(6,930)	(18,703)	(4,910)
Deferred income taxes	8,817	(22,924)	12,110
Stock-based compensation	6,377	10,213	14,784
Equity in net loss from unconsolidated joint ventures	51,486	120,632	44,689
Net income from affiliates	(8,783)	(11,454)	(6,935)
Non-cash impairment charges (see Notes 10 and 12)	156,690	0	0
Other non-cash adjustments	1,729	4,020	4,916
Changes in assets and liabilities, net of the effect of an acquisition in 2019 and 2018:
Receivables	6,840	(58,947)	(9,247)
Contract assets, net	123,670	(40,084)	11,384
Inventories	5,136	380	(2,120)
Contributions to unconsolidated construction joint ventures	(50,878)	(83,765)	(104,333)
Distributions from unconsolidated construction joint ventures and affiliates	11,065	19,064	16,922
Other assets, net	(1,035)	(3,928)	21,619
Accounts payable	(40,999)	140,027	(21,456)
Accrued expenses and other current liabilities, net	49,805	(9,809)	(14,113)
Net cash provided by operating activities	268,460	111,438	86,390
Investing activities
Purchases of marketable securities	(9,996)	0	(9,952)
Maturities of marketable securities	10,000	30,000	75,000
Proceeds from called marketable securities	24,996	0	0
Purchases of property and equipment	(93,253)	(106,828)	(111,101)
Proceeds from sales of property and equipment	16,702	37,091	16,238
Cash paid to purchase business	0	(6,227)	(55,027)
Proceeds from the sale of an investment and business, respectively	5,000	0	47,812
Other investing activities, net	5,289	5,642	(2,568)
Net cash used in investing activities	(41,262)	(40,322)	(39,598)
Financing activities
Proceeds from debt	50,000	105,574	203,250
Proceeds from issuance of 2.75% Convertible Notes, net	0	230,000	0
Proceeds from issuance of warrants, net	0	11,500	0
Purchase of Hedge Option, net	0	(37,375)	0
Debt principal repayments	(83,433)	(313,150)	(153,924)
Cash dividends paid	(23,712)	(24,316)	(22,424)
Repurchases of common stock	(885)	(36,900)	(16,557)
Contributions from non-controlling partners	11,875	68	200
Distributions to non-controlling partners	(11,810)	(12,235)	(13,275)
Debt issuance costs	0	(6,507)	0
Other financing activities, net	307	1,704	856
Net cash used in financing activities	(57,658)	(81,637)	(1,874)
Net increase (decrease) in cash, cash equivalents and restricted cash	169,540	(10,521)	44,918
Cash, cash equivalents and $5,835, $5,825 and $0 in restricted cash at beginning of period	268,108	278,629	233,711
Cash, cash equivalents and $1,512, $5,835 and $5,825 in restricted cash at end of period	437,648	268,108	278,629
Supplementary Information
Right of use assets obtained in exchange for lease obligations	10,000	25,360	0
Cash paid for operating lease liabilities	21,654	18,660	0
Cash paid during the period for:
Interest	18,753	17,322	14,864
Income taxes	2,805	11,898	19,069
Other non-cash operating activities:
Performance guarantees	350	(6,284)	0
Non-cash investing and financing activities:
Reclassification of the equity portion of the 2.75% Convertible Notes from debt to equity (See Note 14)	0	37,375	0
RSUs issued, net of forfeitures	4,449	8,596	13,728
Accrued cash dividends	5,937	5,915	6,068
Common stock issued in acquisition	0	0	321,019
Common stock issued in conversion of 8.0% Convertible Notes	0	0	53,086
Premium on 8.0% Convertible Notes	$ 0	$ 0	$ 30,702