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Stockholders' Equity Stockholders' Equity (Narrative) (Details) - USD ($)
 3 Months Ended 12 Months Ended
Mar. 31, 2018
Dec. 31, 2017
Mar. 31, 2017
Class of Stock [Line Items]      
Preferred Stock, Shares Issued 104,574   104,574
Preferred Stock, Par Value Per Share $ 1.00 $ 1.00  
Preferred Stock, Liquidation Preference Per Share $ 1,000    
Operating Loss Carryforwards   $ 789,700,000  
Common Stock Ownership Enabling Preferred Stock Purchase Rights 4.99%    
Common Stock Ownership Enabling Preferred Stock Purchase Rights, Incremental 0.50%    
Preferred Series B [Member]      
Class of Stock [Line Items]      
Preferred Stock, Shares Issued 104,574 104,574  
Preferred Stock, Par Value Per Share $ 1.00    
Preferred Stock, Liquidation Preference Per Share $ 1,000    
Preferred stock $ 4,600,000 $ 4,600,000  
Preferred Stock, Dividend Rate, Percentage 7.50% 7.50%  
Preferred stock dividend condition - minimum pension funding 90.00%    
Preferred stock dividend condition - minimum net income preceding quarter $ 7,500,000    
Preferred stock dividend condition - minimum free cash flow preceding four quarters 35,000,000    
Preferred stock dividend condition - minimum cash balance preceding quarter 150,000,000    
Preferred Stock, Liquidation Preference, Value 113,500,000 $ 111,500,000  
Preferred Stock, Cumulative Undeclared Dividend $ 6,900,000 $ 6,900,000