Segment Reporting - Information about Segment Assets by Country (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Total assets	$ 3,250,163	$ 3,222,230
Operating Segments [Member] | AEA [Member]
Segment Reporting Information [Line Items]
Total assets	527,583	727,328
Operating Segments [Member] | MEA [Member]
Segment Reporting Information [Line Items]
Total assets	1,383,599	907,936
Operating Segments [Member] | ASA [Member]
Segment Reporting Information [Line Items]
Total assets	713,031	976,470
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Total assets	$ 625,950	$ 610,496