Series A Convertible Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Mar. 17, 2017	Dec. 31, 2016	Dec. 04, 2015
Class of Stock [Line Items]
Series A convertible preferred stock, issued (in shares)	800,000		800,000			900,000
Deemed dividend on preferred stock redemption	$ 0.0	$ 0.0	$ (58.0)	$ 0.0
Deemed dividend on modification of Series A Convertible Preferred Stock	0.0	0.0	(4.0)	0.0
Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Series A convertible preferred stock, issued (in shares)							820,000
Aggregate purchase price of preferred shares							$ 820.0
Preferred Stock, par value (in dollars per share)							$ 1,000
Direct Issuance Expenses							$ 26.0
Dividend rate							5.50%
Payments of Ordinary Dividends, Preferred Stock and Preference Stock	11.0	$ 12.0	34.0	$ 35.0
Accrued Dividends	$ 3.0		$ 3.0			$ 3.0
Conversion Price Per Share At Option Of Holder			$ 30
Conversion rate per preferred share			33.333
Secondary offering by the preferred shareholders					342,000
Redeemed Shares of Preferred stock					90,000
Preferred Stock, Redemption Price Per Share					$ 48.47
Deemed dividend on preferred stock redemption			$ (58.0)
Deemed dividend on modification of Series A Convertible Preferred Stock			$ (4.0)
Financial instruments subject to redemption, settlement terms, maximum number of shares	27,100,000.0		27,100,000.0			29,000,000.0