Condensed Consolidated Balance Sheets (Unaudited) (Parentheticals) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Cash and cash equivalents	$ 393,181	$ 436,136	$ 288,922
Receivables, net	646,940	540,812	596,922
Contract assets	194,483	164,939	191,919
Other current assets	47,976	42,199	57,614
Property and equipment, net	517,143	527,016	540,053
Accounts payable	379,008	359,160	358,401
Contract liabilities	174,850	171,321	159,818
Accrued expenses and other current liabilities	$ 485,718	$ 404,497	$ 363,128
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Preferred stock, authorized (in shares)	3,000,000	3,000,000	3,000,000
Preferred stock, outstanding (in shares)	0	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	150,000,000	150,000,000	150,000,000
Common stock, shares issued (in shares)	45,818,719	45,668,541	45,651,914
Common stock, shares outstanding (in shares)	45,818,719	45,668,541	45,651,914
Consolidated Construction Corporate Joint Venture [Member]
Cash and cash equivalents	$ 107,854	$ 74,819	$ 93,500
Receivables, net	49,408	56,147	31,978
Contract assets	41,815	33,838	26,075
Other current assets	12,142	13,252	14,392
Property and equipment, net	20,206	23,704	27,256
Accounts payable	62,117	53,033	56,315
Contract liabilities	66,193	79,777	69,688
Accrued expenses and other current liabilities	$ 5,186	$ 4,410	$ 4,179