Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Property, plant and equipment	$ 2,916,630		$ 2,916,630		$ 2,757,557
Depreciation expense on property, plant and equipment	$ 52,208	$ 45,080	$ 153,129	$ 123,000