Balance of Investment in Joint Venture (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Capital contributions, net of distributions	$ 4,419	$ 3,420
Equity in cumulative net loss	(2,990)	(259)
Investment in joint venture	$ 1,429	$ 3,161	[1]

[1] Derived from audited financial statements