Nature of Operations and Recent Developments (Pro Forma Share Data After Reverse Stock Split) (Details) - $ / shares shares in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basic and diluted loss per share (in dollars per share)	$ (0.47)	$ (0.14)	$ (0.17)	$ (0.03)	$ (0.31)	$ (0.10)	$ (0.09)	$ (0.11)	$ (0.81)	$ (0.42)	$ (0.64)
Basic and diluted loss per share, pro forma (in dollars per share)									$ (16.11)	$ (8.40)	$ (12.87)
Weighted-average basic and diluted shares (in shares)									75,471	47,580	37,762
Weighted-average basic and diluted shares, pro forma (in shares)									3,774	2,379	1,888