Debt - Deerfield Facility Agreement (Details)						1 Months Ended		3 Months Ended		18 Months Ended
	Apr. 01, 2016 USD ($)	Feb. 05, 2016 USD ($)	Jul. 10, 2015 USD ($)	Nov. 21, 2014 USD ($) $ / shares shares	Mar. 20, 2014 USD ($) $ / shares shares	Apr. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Mar. 31, 2016 USD ($) payment shares	Mar. 31, 2015 USD ($)	Mar. 31, 2016 USD ($) shares	Sep. 01, 2016	Dec. 31, 2015 USD ($)	Mar. 17, 2014 USD ($) $ / shares shares
Line of Credit Facility [Line Items]
Restricted cash								$ 1,250,000		$ 1,250,000		$ 2,350,000
Common stock warrant liabilities								573,000		573,000		$ 687,000
Deerfield [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity													$ 50,000,000
Transaction fee as percentage of principal amount													2.50%
Line of credit				$ 6,000,000	$ 20,000,000			$ 26,200,000		26,200,000
Net proceeds from initial draw under Facility Agreement					19,500,000
Unamortized debt discount				200,000	500,000
Net proceeds from draw under Facility Agreement				$ 5,900,000
Equal annual payments | payment								3
Additional borrowings under the term loan			$ 5,000,000
Second Amendment with Deerfield [Member]
Line of Credit Facility [Line Items]
Debt instrument, stated interest rate		14.75%											8.75%
Portion of interest paid-in-kind, percentage		6.00%
Amendment fee amount		$ 600,000
Amendment fee, installment amount		$ 200,000
Orthotec LLC, Litigation Settlement [Member]
Line of Credit Facility [Line Items]
Payments of settlement						$ 15,750,000	$ 1,750,000
Orthotec LLC, Litigation Settlement [Member] | Deerfield [Member]
Line of Credit Facility [Line Items]
Payments of settlement										$ 24,100,000
Scenario, Forecast [Member] | Second Amendment with Deerfield [Member]
Line of Credit Facility [Line Items]
Portion of interest paid-in-kind, percentage											3.00%
Subsequent event [Member] | Orthotec LLC, Litigation Settlement [Member] | Deerfield [Member]
Line of Credit Facility [Line Items]
Payments of settlement	$ 1,100,000
Initial and Draw Warrants [Member] | Deerfield [Member]
Line of Credit Facility [Line Items]
Warrants outstanding (in shares) | shares								11,450,000		11,450,000
Gain (loss) from change in fair value of warrants								$ 100,000	$ (100,000)
Initial Warrants [Member] | Deerfield [Member]
Line of Credit Facility [Line Items]
Number of securities called by warrants (in shares) | shares													6,250,000
Exercise price of warrants (dollars per share) | $ / shares													$ 1.39
Warrant amount reclassified as debt discount					$ 2,300,000			$ 200,000		$ 200,000
Draw Warrants [Member] | Deerfield [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity													$ 50,000,000
Exercise price of warrants (dollars per share) | $ / shares				$ 1.39	$ 1.39
Line of credit					$ 20,000,000
Number of warrants issued (in shares) | shares				1,200,000	4,000,000
Warrants value				$ 900,000	$ 4,700,000
Draw Warrants [Member] | Maximum [Member] | Deerfield [Member]
Line of Credit Facility [Line Items]
Number of securities called by warrants associated with each disbursement borrowing (in shares) | shares													10,000,000