Stockholder's Equity (Preferred Stock Activity) (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Increase (Decrease) In Stock By Class [Roll Forward]
Preferred stock, beginning balance (in shares)	14,370,060	25,875,000	25,875,000
Shares redeemed (in shares)	0	(11,500,000)	0
Shares converted (in shares)	(95)	(4,940)	0
Preferred stock, ending balance (in shares)	14,369,965	14,370,060	25,875,000	25,875,000
Weighted Average Dividend Rate [Roll Forward]
PreferredStockDividendRatePercentage	6.50%	6.50%	6.50%	6.50%
Preferred stock, weighted avg. dividend rate, shares redeemed	0.00%	6.50%	0.00%
Preferred stock, weighted avg. dividend rate, shares converted	6.50%	6.50%	0.00%
PreferredStockDividendRatePercentage	6.50%	6.50%	6.50%	6.50%