Computation of Gain on Divestiture (Detail) - USD ($) $ in Thousands		4 Months Ended	9 Months Ended
	Jan. 14, 2017	Apr. 22, 2017	Oct. 07, 2017	Dec. 31, 2016
Business Combinations [Abstract]
Cash consideration received	$ 41,230
Recognized amounts of identifiable assets acquired and liabilities assumed:
Property, plant, and equipment recorded as assets held for sale	3,824
Goodwill	801		$ 464,777	$ 465,578
Financial assets	7,730
Net derecognized amounts of identifiable assets sold	12,355
Gain on divestiture	$ 28,875	$ 28,900	$ 28,875