Property, Plant and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Property, Plant and Equipment [Abstract]
Property, plant and equipment	$ 1,952,918		$ 1,952,918		$ 1,510,048
Depreciation expense on property, plant and equipment	$ 32,460	$ 30,055	$ 95,995	$ 90,615