Stockholders' Equity (Stock Redemption) (Details) - USD ($) $ / shares in Units, $ in Thousands					1 Months Ended			12 Months Ended			75 Months Ended	87 Months Ended
	Feb. 26, 2020	Jan. 09, 2020	Oct. 30, 2019	Apr. 30, 2019	Jul. 31, 2018	May 31, 2018	Jan. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2019
Class of Stock [Line Items]
Number of Shares Repurchased (in shares)			446,830	656,433	155,904		373,967	1,103,263			3,288,256	4,391,519
Weighted-Average Price per Share (in usd per share)			$ 17.50	$ 20.25	$ 20.25		$ 21.45	$ 19.14			$ 21.56	$ 20.95
Common stock repurchases			$ 7,800		$ 3,200		$ 8,000	$ 21,113	$ 14,202	$ 33,599
Stock repurchase, value			$ 7,800	$ 13,300		$ 3,000
Subsequent Event
Class of Stock [Line Items]
Number of Shares Repurchased (in shares)	505,101
Weighted-Average Price per Share (in usd per share)	$ 17.50
Stock repurchase, value	$ 8,800	$ 1,700