Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Property, plant and equipment	$ 2,855,508		$ 2,855,508		$ 2,757,557
Depreciation expense on property, plant and equipment	$ 51,263	$ 39,859	$ 100,921	$ 77,920