Stockholders' Equity (Summary of Stock Option Activity and Weighted Average Exercise Prices) (Details) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020 USD ($) $ / shares shares	Dec. 31, 2019 $ / shares shares
Options
Beginning balance (in shares) | shares	5,799
Granted (in shares) | shares	619
Exercised (in shares) | shares	(603)
Cancelled or expired (in shares) | shares	(405)
Ending balance (in shares) | shares	5,410	5,799
Options vested and expected to vest (in shares) | shares	1,603
Options exercisable at end of period (in shares) | shares	2,978
Weighted Average Exercise Price
Beginning balance (in dollars per share) | $ / shares	$ 16.57
Granted (in dollars per share) | $ / shares
Exercised (in dollars per share) | $ / shares
Cancelled or expired (in dollars per share) | $ / shares
Ending balance (in dollars per share) | $ / shares	18.01	$ 16.57
Options vested and expected to vest (in dollars per share) | $ / shares	21.17
Options exercisable at end of period (in dollars per share) | $ / shares	$ 13.98
Weighted Average Remaining Contractual Term (in years)
Weighted average remaining contract term, Options outstanding	6 years 6 months 29 days	6 years 9 months 14 days
Weighted average remaining contract term, Options vested and expected to vest	8 years 4 months 6 days
Weighted average remaining contract term, Options exercisable	4 years 11 months 12 days
Aggregate Intrinsic Value
Aggregate intrinsic value, Options outstanding | $	$ 126,716
Aggregate intrinsic value, Options vested and expected to vest | $	32,477
Aggregate intrinsic value, Options exercisable | $	$ 81,744