Preferred Stock (Series D Preferred Stock) (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended	12 Months Ended
	Feb. 28, 2017	Mar. 16, 2016	Feb. 29, 2012	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Series D Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding						6,245,156
Preferred stock, annual dividend rate		6.25%
Preferred stock, face value		$ 10.00
Conversion price per share	$ 10.40	$ 10.40
Aggregate outstanding shares required for liquidation election		40.00%
Debt instrument conversion ratio to common stock		0.9615385
Series D Preferred Stock [Member] | On Or Before March 16, 2019 [Member]
Class of Stock [Line Items]
Preferred stock, partial redemption value		$ 30,000
Preferred stock, redemption price		$ 12.00
Series D Preferred Stock [Member] | March 16, 2019 to March 16, 2020 [Member]
Class of Stock [Line Items]
Preferred stock, redemption price		13.00
Series D Preferred Stock [Member] | On Or After March 16, 2020 [Member]
Class of Stock [Line Items]
Preferred stock, redemption price		$ 14.00
Series D Preferred Stock [Member] | On Or Before September 30, 2021 [Member]
Class of Stock [Line Items]
Aggregate outstanding shares required for liquidation election		40.00%
Preferred stock, redemption price		$ 14.00
Series D Preferred Stock [Member] | After September 30, 2021 [Member]
Class of Stock [Line Items]
Preferred stock, annual dividend rate		12.50%
Series C Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares issued			3,000,000
Preferred stock, annual dividend rate			6.25%
Series E Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, value				$ 10,050	$ 10,050
Preferred stock, shares outstanding	925,000			925,000	925,000
Preferred stock, annual dividend rate	6.25%			6.25%
Preferred stock, face value	$ 10.00
Shares issued upon conversion	925,000
Conversion price per share	$ 13.845
Shares issued upon conversion, amount	$ 9,250
Minimum [Member] | Series D Preferred Stock [Member]
Class of Stock [Line Items]
Debt instrument conversion amount upon closing of qualified offering		$ 50,000
Maximum [Member] | Series D Preferred Stock [Member]
Class of Stock [Line Items]
Debt instrument conversion amount upon closing of qualified offering		$ 75,000
Common Stock [Member]
Class of Stock [Line Items]
Shares issued upon conversion	6,004,957
Shares issued, price per share	$ 10.40