Investments and Fair Value of Financial Instruments - Summary of Changes in Fair Value and Other Adjustments of Derivative Liabilities (Detail) - Derivative Financial Instruments Liabilities [Member] - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2015
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 2,979	$ 1,580
Change in fair value and other adjustments	(291)	1,108
Ending balance	$ 2,688	$ 2,688