Stockholders' Equity (At-the-Market) (Details) - At The Market - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Aug. 16, 2019
Class of Stock [Line Items]
At-the-market, maximum potential proceeds			$ 400,000
Sales commission, percent of gross sales price			2.00%
Number of shares issued (in shares)	0	1,357,526
Value remaining outstanding for future offerings	$ 390,000
Gross proceeds (usd per share)		$ 7.40
Proceeds from sale of stock		$ 9,900
Debt issuance fees		$ 100