Discontinued Operations - Assets and Liabilities Held for Sale (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Contract assets	$ 1,310,686	$ 1,238,173
Other accrued liabilities	425,897	470,351
Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accounts and notes receivable, net	65,230	85,051
Contract assets	3,930	3,497
Other current assets	46,014	54,116
Current assets held for sale	115,174	142,664
Property, plant and equipment, net	132,315	232,792
Goodwill	37	12,338
Investments	0	0
Other assets	5,135	5,868
Noncurrent assets held for sale	137,487	250,998
Total assets held for sale	252,661	393,662
Accounts payable	14,446	24,692
Contract liabilities	2,462	4,466
Accrued salaries, wages and benefits	8,177	8,913
Other accrued liabilities	8,065	9,451
Current liabilities held for sale	33,150	47,522
Noncurrent liabilities held for sale	3,638	4,272
Total liabilities held for sale	36,788	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	49,305	69,126
Contract assets	3,930	3,497
Other current assets	46,014	54,116
Current assets held for sale	99,249	126,739
Property, plant and equipment, net	132,315	232,792
Goodwill	37	12,338
Investments	0	0
Other assets	5,135	5,868
Noncurrent assets held for sale	137,487	250,998
Total assets held for sale	236,736	377,737
Accounts payable	14,438	24,692
Contract liabilities	2,462	4,466
Accrued salaries, wages and benefits	8,177	8,913
Other accrued liabilities	7,604	9,451
Current liabilities held for sale	32,681	47,522
Noncurrent liabilities held for sale	3,638	4,272
Total liabilities held for sale	36,319	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	8	0
Contract liabilities	0	0
Accrued salaries, wages and benefits	0	0
Other accrued liabilities	461	0
Current liabilities held for sale	469	0
Noncurrent liabilities held for sale	0	0
Total liabilities held for sale	469	0
Continuing Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accounts and notes receivable, net	14,927	17,513
Contract assets	4,603	3,779
Other current assets	7,029	8,112
Current assets held for sale	26,559	29,404
Property, plant and equipment, net	59,683	106,762
Goodwill	7,311	9,295
Investments	6,118	7,293
Other assets	14,307	12,654
Noncurrent assets held for sale	87,419	136,004
Total assets held for sale	113,978	165,408
Accounts payable	7,384	6,702
Contract liabilities	55	25
Accrued salaries, wages and benefits	118	919
Other accrued liabilities	10,288	11,562
Current liabilities held for sale	17,845	19,208
Noncurrent liabilities held for sale	10,706	11,320
Total liabilities held for sale	28,551	30,528
Total
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accounts and notes receivable, net	80,157	102,564
Contract assets	8,533	7,276
Other current assets	53,043	62,228
Current assets held for sale	141,733	172,068
Property, plant and equipment, net	191,998	339,554
Goodwill	7,348	21,633
Investments	6,118	7,293
Other assets	19,442	18,522
Noncurrent assets held for sale	224,906	387,002
Total assets held for sale	366,639	559,070
Accounts payable	21,830	31,394
Contract liabilities	2,517	4,491
Accrued salaries, wages and benefits	8,295	9,832
Other accrued liabilities	18,353	21,013
Current liabilities held for sale	50,995	66,730
Noncurrent liabilities held for sale	14,344	15,592
Total liabilities held for sale	$ 65,339	$ 82,322