Equity (Details) - USD ($) $ / shares in Units, $ in Thousands				12 Months Ended
	Sep. 22, 2017	Oct. 11, 2016	Sep. 27, 2012	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Stock Repurchase
Repurchase of common stock authorized by Board of Directors			$ 100,000	$ 60,000
Number of years for repurchase of common stock			5 years
Common stock repurchased, value				$ 16,205	$ 3,546	$ 28,958
Shares issued				2,500,000	2,500,000
Par value				$ 0.01	$ 0.01
Dividend rate (as a percent)				6.50%
Liquidation preference				$ 20.00
Redemption price				$ 20.00
Common Stock
Common Stock Repurchase
Common stock repurchased (in shares)				472,000	155,312	1,212,000
Common stock repurchased, value				$ 5	$ 2	$ 12
Preferred Stock
Common Stock Repurchase
Shares issued					1,500,000	1,000,000
Redeemable Preferred Stock
Common Stock Repurchase
Shares issued		1,000,000
Par value		$ 0.01
Dividend rate (as a percent)		6.50%
Purchase price		$ 20.00
Net proceeds after deducting investor fees				19,800
Series A-1 Preferred Stock
Common Stock Repurchase
Preferred stock dividends paid				3,200
Series A-2 Preferred Stock
Common Stock Repurchase
Shares issued	1,500,000
Par value	$ 0.01
Dividend rate (as a percent)	6.50%
Purchase price	$ 20.00
Net proceeds after deducting investor fees				$ 29,700
Preferred stock dividends paid					$ 1,300
Dutch Auction
Common Stock Repurchase
Weighted average price per share (in dollars per share)				$ 34.36	$ 22.83