Discontinued Operations - Assets and Liabilities Held for Sale (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Contract assets	$ 1,069,507	$ 1,238,173
Other accrued liabilities	62,278	82,322
Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accounts and notes receivable, net	71,674	85,051
Contract assets	2,157	3,497
Other current assets	45,109	54,116
Current assets held for sale	118,940	142,664
Property, plant and equipment, net	131,567	232,792
Goodwill	37	12,338
Investments	0	0
Other assets	9,014	5,868
Noncurrent assets held for sale	140,618	250,998
Total assets held for sale	259,558	393,662
Accounts payable	10,907	24,692
Contract liabilities	139	4,466
Accrued salaries, wages and benefits	7,772	8,913
Other accrued liabilities	11,744	9,451
Current liabilities held for sale	30,562	47,522
Noncurrent liabilities held for sale	6,283	4,272
Total liabilities held for sale	36,845	51,794
Discontinued Operations | AMECO
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accounts and notes receivable, net	55,749	69,126
Contract assets	2,157	3,497
Other current assets	45,109	54,116
Current assets held for sale	103,015	126,739
Property, plant and equipment, net	131,567	232,792
Goodwill	37	12,338
Investments	0	0
Other assets	9,014	5,868
Noncurrent assets held for sale	140,618	250,998
Total assets held for sale	243,633	377,737
Accounts payable	10,884	24,692
Contract liabilities	139	4,466
Accrued salaries, wages and benefits	7,772	8,913
Other accrued liabilities	11,744	9,451
Current liabilities held for sale	30,539	47,522
Noncurrent liabilities held for sale	6,283	4,272
Total liabilities held for sale	36,822	51,794
Discontinued Operations | Other
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accounts and notes receivable, net	15,925	15,925
Contract assets	0	0
Other current assets	0	0
Current assets held for sale	15,925	15,925
Property, plant and equipment, net	0	0
Goodwill	0	0
Investments	0	0
Other assets	0	0
Noncurrent assets held for sale	0	0
Total assets held for sale	15,925	15,925
Accounts payable	23	0
Contract liabilities	0	0
Accrued salaries, wages and benefits	0	0
Other accrued liabilities	0	0
Current liabilities held for sale	23	0
Noncurrent liabilities held for sale	0	0
Total liabilities held for sale	23	0
Continuing Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accounts and notes receivable, net	11,913	17,513
Contract assets	4,177	3,779
Other current assets	6,677	8,112
Current assets held for sale	22,767	29,404
Property, plant and equipment, net	59,132	64,792
Goodwill	6,087	9,295
Investments	6,838	7,293
Other assets	14,453	12,654
Noncurrent assets held for sale	86,510	94,034
Total assets held for sale	109,277	123,438
Accounts payable	7,739	6,702
Contract liabilities	25	25
Accrued salaries, wages and benefits	107	919
Other accrued liabilities	6,981	11,562
Current liabilities held for sale	14,852	19,208
Noncurrent liabilities held for sale	10,581	11,320
Total liabilities held for sale	25,433	30,528
Total
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accounts and notes receivable, net	83,587	102,564
Contract assets	6,334	7,276
Other current assets	51,786	62,228
Current assets held for sale	141,707	172,068
Property, plant and equipment, net	190,699	297,584
Goodwill	6,124	21,633
Investments	6,838	7,293
Other assets	23,467	18,522
Noncurrent assets held for sale	227,128	345,032
Total assets held for sale	368,835	517,100
Accounts payable	18,646	31,394
Contract liabilities	164	4,491
Accrued salaries, wages and benefits	7,879	9,832
Other accrued liabilities	18,725	21,013
Current liabilities held for sale	45,414	66,730
Noncurrent liabilities held for sale	16,864	15,592
Total liabilities held for sale	$ 62,278	$ 82,322