Preferred Stock Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Millions				12 Months Ended
	Mar. 12, 2015	Dec. 31, 2011	Sep. 30, 2009	Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Par value				$ 1.00	$ 1.00
Series 2009 Preferred Stock [Member]
Class of Stock [Line Items]
Shares issued			3,710
Preferred stock, including additional paid in capital			$ 3.7
Dividend rate	8.00%		8.00%
Par value	$ 1.00		$ 1.00
Liquidation preference per share	$ 1,000		$ 1,000
Series 2011 Preferred Stock [Member]
Class of Stock [Line Items]
Shares issued		12,000
Preferred stock, including additional paid in capital		$ 6.0
Dividend rate	8.00%	8.00%
Par value	$ 1.00	$ 1.00
Liquidation preference per share	$ 500	$ 500
Preferred Non-Convertible Stock [Member]
Class of Stock [Line Items]
Dividend rate				8.00%