Common Stock and Other Equity Related Transactions - ATM Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Class of Stock
Shares in common stock sold (in shares)	0	1,010,472	1,722,282
Total gross proceeds	$ 0	$ 59,319	$ 78,755
Commissions paid to sales agents	$ 673	$ 1,347	$ 1,651
Private Placement | Common Stock
Class of Stock
Shares in common stock sold (in shares)	0	1,010,472	1,722,282
Weighted average price (usd per share)	$ 0	$ 58.71	$ 45.73
Total gross proceeds	$ 0	$ 59,319	$ 78,755
Commissions paid to sales agents	$ 0	$ 771	$ 1,028