Stock-Based Compensation Nonvested Restricted Stocks (Details) - Restricted stock and restricted stock units - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Shares
Nonvested at beginning period (in shares)	309	308	218
Granted (in shares)	577	230	279
Vested (in shares)	(244)	(198)	(186)
Canceled (in shares)	(114)	(31)	(3)
Nonvested at period end (in shares)	528	309	308
Weighted Average Grant-Date Fair Value
Nonvested at beginning period (in dollars per share)	$ 2.87	$ 2.38	$ 3.87
Granted (in dollars per share)	4.50	3.16	2.17
Vested (in dollars per share)	2.23	2.53	3.66
Canceled (in dollars per share)	3.22	2.25	14.78
Nonvested at period end (in dollars per share)	$ 4.52	$ 2.87	$ 2.38