Investments and Fair Value Measurements - Summary of Changes in Fair Value and Other Adjustments of Derivative Liabilities (Detail) - Derivative Financial Instruments Liabilities [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 0	$ 1,580
Change in fair value and other adjustments	0	9
Derecognition of derivative liabilities upon debt extinguishment	0	(1,589)
Ending balance	$ 0	$ 0