Notes Payable - Essex Capital Notes (Detail) - USD ($)	1 Months Ended			2 Months Ended	12 Months Ended
	Jun. 30, 2015	Feb. 28, 2015	May. 31, 2014	Jan. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 17, 2014	Feb. 28, 2014	Dec. 20, 2013
Debt Instrument [Line Items]
Settlement of outstanding loan balance					$ 0	$ 0	$ 32,008,000
Interest expense for amortization of warrant					1,190,000	10,672,000	15,164,000
Interest paid					$ 802,000	$ 1,182,000	1,590,000
Warrants
Debt Instrument [Line Items]
Number of shares called by warrant					61,595	198,662
Essex Notes
Debt Instrument [Line Items]
Secured promissory notes, able to borrow (up to)										$ 10,800,000
Interest rate, percentage									10.375%	11.50%
Short-term notes				$ 2,500,000			$ 2,500,000
Settlement of outstanding loan balance			$ 1,100,000
Lease period		3 years	3 years
Total principal payments								$ 3,900,000
Number of shares called by warrant								44,753
Equipment Purchased by Third Party, Increase During Period		$ 100,000
Equipment purchased by third party		$ 9,800,000
Percentage of original purchase amount of asset at end of lease		10.00%
Purchase of equipment sold and leased back	$ 1,100,000
Common stock shares purchased (in shares)				12,345
Fair value of warrants						$ 200,000
Debt issuance costs					$ 30,000
Unamortized debt discount						0
Interest paid					0	400,000
Essex Notes | Warrants
Debt Instrument [Line Items]
Interest expense for amortization of warrant					$ 0	$ 200,000