Stock-Based Compensation (Restricted Stock Units Activity) (Details) - Restricted Stock Units (RSUs) shares in Thousands	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Number of Shares
Beginning balance (in shares) | shares	6,100
Granted (in shares) | shares	5,341
Canceled (in shares) | shares	(506)
Vested (in shares) | shares	(2,858)
Ending balance (in shares) | shares	8,077
Weighted-Average Grant Date Fair Value
Beginning balance (in dollars per share) | $ / shares	$ 3.56
Granted (in dollars per share) | $ / shares	5.09
Canceled (in dollars per share) | $ / shares	3.94
Vested (in dollars per share) | $ / shares	3.82
Ending balance (in dollars per share) | $ / shares	$ 4.46