Series A Convertible Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 04, 2015
Class of Stock [Line Items]
Series A convertible preferred stock, issued (in shares)	900,000		800,000	820,000
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	$ 12.0	$ 12.0
Accrued Dividends	$ 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
Financial instruments subject to redemption, settlement terms, maximum number of shares	26,400,000.0		29,000,000.0
Deemed dividend on preferred stock redemption	$ (58.0)	$ 0.0
Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Aggregate purchase price of preferred shares				$ 820.0