Stockholders' Equity (Summary of Restricted Stock Unit Activity and Weighted Average Exercise Price) (Details) - Restricted Stock Units (RSUs) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Number of Shares (in thousands)
Beginning balance outstanding (in shares)	3,049
Awarded (in shares)	2,294
Released (in shares)	(1,503)
Forfeited (in shares)	(490)
Non-vested and outstanding at end of period (in shares)	3,350
Expected to vest (in shares)	2,048
Weighted Average Grant Date Fair Value (usd per share)
Beginning balance outstanding (in dollars per share)	$ 24.73
Awarded (in dollars per share)
Released (in dollars per share)
Forfeited (in dollars per share)
Non-vested and outstanding at end of period (in dollars per share)	24.89
Expected to vest (in dollars per share)	$ 24.16
Aggregate Fair Value (in thousands)
Aggregate fair value, Non-vested and outstanding	$ 138,789	$ 112,848
Aggregate fair value, Expected to vest	$ 84,850