Income Taxes (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Research and development tax credits	$ 16,364,000	$ 18,507,000
Valuation Allowance, Deferred Tax Asset, Change in Amount	7,913,000	24,233,000	$ (63,868,000)
Income tax benefit	$ 0	$ 0	$ 0
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate	21.00%	21.00%	34.00%
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	$ 646,300,000
Operating loss carryforwards that do not expire	38,600,000
Research and development tax credits	$ 8,800,000
Internal Revenue Service (IRS) [Member] | Minimum [Member]
Operating Loss Carryforwards [Line Items]
Research and development tax credits expiration year	2020
Internal Revenue Service (IRS) [Member] | Maximum [Member]
Operating Loss Carryforwards [Line Items]
Research and development tax credits expiration year	2033
Federal and State [Member] | Minimum [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards expiration year	2021
Federal and State [Member] | Maximum [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards expiration year	2038
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	$ 184,900,000
Research and development tax credits	9,400,000
Investment tax credit	$ 214,000
State and Local Jurisdiction [Member] | Minimum [Member]
Operating Loss Carryforwards [Line Items]
Research and development tax credits expiration year	2020
Investment tax credit expiration year	2020
State and Local Jurisdiction [Member] | Maximum [Member]
Operating Loss Carryforwards [Line Items]
Research and development tax credits expiration year	2029
Investment tax credit expiration year	2022
Foreign Tax Authority [Member] | Minimum [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards expiration year	2024
Foreign Tax Authority [Member] | Maximum [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards expiration year	2026
Foreign Tax Authority [Member] | Switzerland [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	$ 1,900,000
Foreign Tax Authority [Member] | United Kingdom [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	7,500,000
Foreign Tax Authority [Member] | Belgium [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	8,000,000
Foreign Tax Authority [Member] | Ireland [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	55,000
Foreign Tax Authority [Member] | Hong Kong [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	289,000
Worldwide [Member]
Operating Loss Carryforwards [Line Items]
Valuation Allowance, Deferred Tax Asset, Change in Amount	$ 7,900,000	$ (21,900,000)