Equity Offerings - Narrative (Details) - Distribution Agreement - USD ($) $ / shares in Units, shares in Thousands		3 Months Ended	6 Months Ended
	Nov. 03, 2017	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2020
Subsidiary, Sale of Stock [Line Items]
Maximum aggregate offering price	$ 125,000,000.0
Gross proceeds from sales of common stock		$ 17,900,000	$ 38,500,000
Issuance costs on sales of common stock		$ 300,000	$ 700,000
Number of shares sold (in shares)		217	460
Price per share sold (in dollars per share)		$ 82.51	$ 83.81
Aggregate value of shares available to be offered				$ 31,500,000