Equity - Convertible Preferred Stock Table (Details) - shares	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Preferred stock, shares outstanding, beginning of period	7,251,515
Preferred stock, shares outstanding, end of period	7,225,713
Preferred stock, shares outstanding, beginning and end of period	7,251,515
Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Conversion of Stock, Shares Converted	25,802	0
5.75% Cumulative Convertible Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred Stock, Dividend Rate, Percentage	5.75%
Stock Issued During Period, Shares, Conversion of Convertible Securities	975,488
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Preferred stock, shares outstanding, beginning of period	1,497,000	1,497,000
Preferred stock, shares outstanding, end of period	1,472,000	1,497,000
Preferred stock, shares outstanding, beginning and end of period	1,497,000	1,497,000
5.75% Cumulative Convertible Preferred Stock [Member] | Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Conversion of Stock, Shares Converted	25,000
5.75% Cumulative Convertible Preferred Stock Series A [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred Stock, Dividend Rate, Percentage	5.75%
Stock Issued During Period, Shares, Conversion of Convertible Securities	46,018
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Preferred stock, shares outstanding, beginning of period	1,100,000	1,100,000
Preferred stock, shares outstanding, end of period	1,099,000	1,100,000
Preferred stock, shares outstanding, beginning and end of period	1,100,000	1,100,000
5.75% Cumulative Convertible Preferred Stock Series A [Member] | Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Conversion of Stock, Shares Converted	1,000
4.50% Cumulative Convertible Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Preferred stock, shares outstanding, beginning of period	2,559,000	2,559,000
Preferred stock, shares outstanding, end of period	2,559,000	2,559,000
Preferred stock, shares outstanding, beginning and end of period	2,559,000	2,559,000
4.50% Cumulative Convertible Preferred Stock [Member] | Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Conversion of Stock, Shares Converted	0
5.0% Cumulative Convertible Preferred Stock Series 2005 B [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Preferred stock, shares outstanding, beginning of period	2,096,000	2,096,000
Preferred stock, shares outstanding, end of period	2,096,000	2,096,000
Preferred stock, shares outstanding, beginning and end of period	2,096,000	2,096,000
5.0% Cumulative Convertible Preferred Stock Series 2005 B [Member] | Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Conversion of Stock, Shares Converted	0