Plant and Equipment - Plant and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Property, Plant and Equipment [Abstract]
Work in process	$ 207
Plant and equipment at cost	55,271		55,271
Less accumulated depreciation	(32,639)		(28,836)
Net book value	22,839		26,435
Total depreciation expense on plant and equipment	$ 3,803	$ 4,698