Information Pertaining to 2022 Notes (Detail)	12 Months Ended
	Dec. 31, 2016 USD ($)
Debt Instrument [Line Items]
Beginning balance	$ 14,341,000
Beginning balance	(2,000)
Ending balance	8,221,000
2022 Notes
Debt Instrument [Line Items]
Beginning balance	14,341,000
Amortization of debt discount	4,026,000
Amortization of debt issue costs	156,000
Exchange of 2022 Notes	(12,825,000)
Write-off of debt discount and debt issue costs associated with extinguishment of debt	2,523,000
Ending balance	8,221,000
2022 Notes | Principal Amount of 2022 Notes
Debt Instrument [Line Items]
Beginning balance	22,400,000
Exchange of 2022 Notes	(12,825,000)
Ending balance	9,575,000
2022 Notes | Debt Discount
Debt Instrument [Line Items]
Beginning balance	(7,764,000)
Amortization of debt discount	4,026,000
Write-off of debt discount and debt issue costs associated with extinguishment of debt	2,431,000
Ending balance	(1,307,000)
2022 Notes | Debt Issue Costs
Debt Instrument [Line Items]
Beginning balance	(295,000)
Amortization of debt issue costs	156,000
Write-off of debt discount and debt issue costs associated with extinguishment of debt	92,000
Ending balance	$ (47,000)