Segment Reporting - Information about Operations in Different Segments (Parenthetical) (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Capital expenditures	[1]	$ 18,386	$ 62,849
Amazon Pipelay and Construction Vessel [Member]
Segment Reporting Information [Line Items]
Bareboat charter agreement, term			11 years
Liability Associated with Assets [Member]
Segment Reporting Information [Line Items]
Capital expenditures		10,000	$ 9,000
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Restructuring costs and transaction costs related to the combination		14,000	14,000
Gain on sale of assets		3,000	3,000
Capital expenditures	[1],[2]	$ 9,528	$ 48,234

[1] Liabilities associated with assets acquired during the first quarter of 2018 and 2017 were $10 million and $9 million, respectively.

[2] Corporate and other capital expenditures in the first quarter of 2017 include the purchase of the Amazon, a pipelay and construction vessel. Following the purchase, we sold this vessel to an unrelated party and simultaneously entered into an 11-year bareboat charter agreement.