Cash and Cash Equivalents (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash And Cash Equivalents [Abstract]
Cash and other bank balances	$ 422,623	$ 450,907
Total	$ 422,623	$ 450,907	$ 461,788	$ 571,276