Segment Reporting - Information about Segment Assets by Country (Detail) - USD ($) $ in Thousands		Sep. 30, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Total assets	[1]	$ 3,461,435	$ 3,222,230
Operating Segments [Member] | AEA [Member]
Segment Reporting Information [Line Items]
Total assets	[1]	695,751	727,328
Operating Segments [Member] | MEA [Member]
Segment Reporting Information [Line Items]
Total assets	[1]	1,632,064	907,936
Operating Segments [Member] | ASA [Member]
Segment Reporting Information [Line Items]
Total assets	[1]	671,864	976,470
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Total assets	[1]	$ 461,756	$ 610,496

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