Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended	9 Months Ended
		Mar. 31, 2016	Sep. 30, 2016	Sep. 30, 2017	Dec. 31, 2016
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Aggregate carrying value of assets	[1]			$ 3,461,435	$ 3,222,230
ASA [Member] | Marine Assets [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Non-cash impairment charges			$ 12,000
Aggregate carrying value of assets			22,000
Estimated fair value of assets			$ 10,000
AEA [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Non-cash impairment charges		$ 32,000

[1] Our marine vessels are included in the area in which they were located as of reporting date.