Fair Value Measurements (Assets and Liabilities Measured on Recurring Basis) (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Jun. 26, 2019
Liabilities:
Warrants issued	$ 2,831	$ 7,725	$ 10,798
Level 1
Assets:
Money market funds, stable net asset value per share (in dollars per share)	$ 1.00
Recurring
Assets:
Total	$ 11,928	25,336
Liabilities:
Financing derivatives: no hedging designation	15,002	29,312
Recurring | Interest Make-whole Derivative Liability
Liabilities:
Secured term note	871	0
Recurring | No hedging designation | Interest rate reset
Liabilities:
Financing derivatives: no hedging designation	11,300	18,800
Recurring | No hedging designation | Make-whole change of control
Liabilities:
Financing derivatives: no hedging designation	0	1,600
Recurring | No hedging designation | Qualifying change of control
Liabilities:
Financing derivatives: no hedging designation	0	1,187
Recurring | Money market funds
Assets:
Cash and cash equivalent assets	11,928	24,327
Recurring | Certificates of deposit
Assets:
Cash and cash equivalent assets	0	1,009
Recurring | Level 1
Assets:
Total	11,928	24,327
Liabilities:
Financing derivatives: no hedging designation	0	0
Recurring | Level 1 | Interest Make-whole Derivative Liability
Liabilities:
Secured term note	0	0
Recurring | Level 1 | No hedging designation | Interest rate reset
Liabilities:
Financing derivatives: no hedging designation	0	0
Recurring | Level 1 | No hedging designation | Make-whole change of control
Liabilities:
Financing derivatives: no hedging designation	0	0
Recurring | Level 1 | No hedging designation | Qualifying change of control
Liabilities:
Financing derivatives: no hedging designation	0	0
Recurring | Level 1 | Money market funds
Assets:
Cash and cash equivalent assets	11,928	24,327
Recurring | Level 1 | Certificates of deposit
Assets:
Cash and cash equivalent assets	0	0
Recurring | Level 2
Assets:
Total	0	1,009
Liabilities:
Financing derivatives: no hedging designation	0	0
Recurring | Level 2 | Interest Make-whole Derivative Liability
Liabilities:
Secured term note	0	0
Recurring | Level 2 | No hedging designation | Interest rate reset
Liabilities:
Financing derivatives: no hedging designation	0	0
Recurring | Level 2 | No hedging designation | Make-whole change of control
Liabilities:
Financing derivatives: no hedging designation	0	0
Recurring | Level 2 | No hedging designation | Qualifying change of control
Liabilities:
Financing derivatives: no hedging designation	0	0
Recurring | Level 2 | Money market funds
Assets:
Cash and cash equivalent assets	0	0
Recurring | Level 2 | Certificates of deposit
Assets:
Cash and cash equivalent assets	0	1,009
Recurring | Level 3
Assets:
Total	0	0
Liabilities:
Financing derivatives: no hedging designation	15,002	29,312
Recurring | Level 3 | Interest Make-whole Derivative Liability
Liabilities:
Secured term note	871	0
Recurring | Level 3 | No hedging designation | Interest rate reset
Liabilities:
Financing derivatives: no hedging designation	11,300	18,800
Recurring | Level 3 | No hedging designation | Make-whole change of control
Liabilities:
Financing derivatives: no hedging designation	0	1,600
Recurring | Level 3 | No hedging designation | Qualifying change of control
Liabilities:
Financing derivatives: no hedging designation	0	1,187
Recurring | Level 3 | Money market funds
Assets:
Cash and cash equivalent assets	0	0
Recurring | Level 3 | Certificates of deposit
Assets:
Cash and cash equivalent assets	0	0
Series A Warrants
Liabilities:
Warrants issued			3,862
Series A Warrants | Recurring
Liabilities:
Warrants issued	2,831	7,508
Series A Warrants | Recurring | Level 1
Liabilities:
Warrants issued	0	0
Series A Warrants | Recurring | Level 2
Liabilities:
Warrants issued	0	0
Series A Warrants | Recurring | Level 3
Liabilities:
Warrants issued	2,831	7,508
Series B-2 Warrant
Liabilities:
Warrants issued			$ 376
Series B-2 Warrant | Recurring
Liabilities:
Warrants issued	0	217
Series B-2 Warrant | Recurring | Level 1
Liabilities:
Warrants issued	0	0
Series B-2 Warrant | Recurring | Level 2
Liabilities:
Warrants issued	0	0
Series B-2 Warrant | Recurring | Level 3
Liabilities:
Warrants issued	$ 0	$ 217