Earnings per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Net income (loss)	$ (24.7)	$ 38.9
Less: Net income attributable to noncontrolling interests	14.2	16.0
Less: Dividends on preferred stock	30.8	29.9
Net income (loss) attributable to common shareholders	$ (69.7)	$ (7.0)
Weighted average shares outstanding - basic (in shares)	232.2	218.7
Net income available per common share - basic (in dollars per share)	$ (0.30)	$ (0.03)
Weighted average shares outstanding - basic (in shares)	232.2	218.7
Weighted average shares outstanding - diluted (in shares)	232.2	218.7
Net income available per common share - diluted (in dollars per share)	$ (0.30)	$ (0.03)