Debt - Interest Expense (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Convertible Notes [Member]
Debt Instrument [Line Items]
Interest expense-stated coupon rate	$ 6,108	$ 307
Interest expense - amortization/appreciation of debt discount/premium	4,492	260
Total interest expense-Cabot Notes	10,600	567
Cabot Senior Secured Notes [Member]
Debt Instrument [Line Items]
Interest expense-stated coupon rate	27,496
Interest expense - amortization/appreciation of debt discount/premium	(2,826)
Total interest expense-Cabot Notes	$ 24,670