Restructuring - Restructuring Costs Incurred and Future Cost Expected to be Incurred (Detail) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Incurred for the period	$ 1,836,000	$ 0	$ 10,687,000
Incurred from inception to September 30, 2017		99,321,000
Americas Restructuring [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Incurred for the period			(1,500,000)
Incurred from inception to September 30, 2017		44,194,000
McDermott Profitability Initiative [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Incurred for the period	1,165,000		5,248,000
Incurred from inception to September 30, 2017		46,962,000
McDermott Profitability Initiative [Member] | Severance and other personnel-related costs [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Incurred for the period	1,165,000		2,590,000
Incurred from inception to September 30, 2017		17,807,000
McDermott Profitability Initiative [Member] | Asset impairment and disposal [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Incurred from inception to September 30, 2017		7,471,000
McDermott Profitability Initiative [Member] | Legal and other advisor fees [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Incurred for the period			222,000
Incurred from inception to September 30, 2017		11,639,000
McDermott Profitability Initiative [Member] | Other Charges [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Incurred for the period			2,436,000
Incurred from inception to September 30, 2017		10,045,000
Additional Overhead Reduction [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Incurred for the period	671,000		6,939,000
Incurred from inception to September 30, 2017		8,165,000
Additional Overhead Reduction [Member] | Severance and other personnel-related costs [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Incurred for the period	556,000		4,600,000
Incurred from inception to September 30, 2017		5,012,000
Additional Overhead Reduction [Member] | Legal and other advisor fees [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Incurred for the period			1,968,000
Incurred from inception to September 30, 2017		2,768,000
Additional Overhead Reduction [Member] | Other Charges [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Incurred for the period	$ 115,000		$ 371,000
Incurred from inception to September 30, 2017		$ 385,000