Property, Plant and Equipment - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended	109 Months Ended
	Mar. 31, 2013	Mar. 31, 2013	Jun. 30, 2014	Dec. 31, 2013
Property Plant And Equipment [Line Items]
Construction in progress			$ 65.7	$ 65.7
Capitalized interest expense	$ 0.1	$ 0.1	$ 1.8