Stock Benefit Plans and Equity Transactions - Summary Common Stock Reserved for Future Issuance (Details) shares in Thousands	Sep. 30, 2018 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Common stock reserved for future issuance	38,208
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Common stock reserved for future issuance	4,880
Unvested restricted share awards
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Common stock reserved for future issuance	3,542
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Common stock reserved for future issuance	232
Series A Convertible Preferred Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Common stock reserved for future issuance	2,022
Convertible Notes
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Common stock reserved for future issuance	988
Warrants Outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Common stock reserved for future issuance	20,932
Distributor and surgeon royalty plans
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Common stock reserved for future issuance	4,000
Merger contingently issuable
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Common stock reserved for future issuance	887
Authorized for future grant under the company equity plans
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Common stock reserved for future issuance	725