Income Taxes (Schedule of Federal Net Operating Losses and Tax Credit Carryforwards) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Net Operating Losses	$ 142,674
Research and Development Tax Credits	2,479	$ 2,438
2019-2020 [Member]
Operating Loss Carryforwards [Line Items]
Net Operating Losses	24,931
Research and Development Tax Credits	653
2021-2024 [Member]
Operating Loss Carryforwards [Line Items]
Net Operating Losses	41,283
2025-2037 [Member]
Operating Loss Carryforwards [Line Items]
Net Operating Losses	61,755
Research and Development Tax Credits	1,826
No Expiration [Member]
Operating Loss Carryforwards [Line Items]
Net Operating Losses	$ 14,705
Minimum [Member] | 2019-2020 [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, expiration	Jan. 01, 2019
Minimum [Member] | 2021-2024 [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, expiration	Jan. 01, 2021
Minimum [Member] | 2025-2037 [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, expiration	Jan. 01, 2025
Maximum [Member] | 2019-2020 [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, expiration	Dec. 31, 2020
Maximum [Member] | 2021-2024 [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, expiration	Dec. 31, 2024
Maximum [Member] | 2025-2037 [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, expiration	Dec. 31, 2037