Debt - Interest Expense (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Convertible Notes [Member]
Debt Instrument [Line Items]
Interest expense—stated coupon rate	$ 3,316	$ 2,141	$ 9,080	$ 3,947
Interest expense—amortization of debt discount	2,228	1,570	6,164	2,887
Total interest expense—convertible notes	5,544	3,711	15,244	6,834
Cabot and Marlin Acquisitions [Member]
Debt Instrument [Line Items]
Interest expense—stated coupon rate	26,239	12,857	72,099	12,857
Interest expense—amortization of debt discount	(2,760)	(1,367)	(7,565)	(1,367)
Total interest expense—convertible notes	$ 23,479	$ 11,490	$ 64,534	$ 11,490