Earnings per Common Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Net income (loss)	$ 177.1	$ 48.9	$ (1,643.2)	$ 24.2
Less: Net income attributable to noncontrolling interests	96.1	59.1	13.6	73.3
Less: Dividends on preferred stock	32.1	31.0	64.0	61.8
Net income (loss) attributable to common shareholders	$ 48.9	$ (41.2)	$ (1,720.8)	$ (110.9)
Weighted average shares outstanding - basic (in shares)	233,100,000	232,400,000	233,100,000	232,300,000
Net income (loss) available per common share - basic (in dollars per share)	$ 0.21	$ (0.18)	$ (7.38)	$ (0.48)
Weighted average shares outstanding - basic (in shares)	233,100,000	232,400,000	233,100,000	232,300,000
Diluted effect of unvested stock awards	0.7
Weighted average shares outstanding - diluted (in shares)	233,800,000	232,400,000	233,100,000	232,300,000
Net income (loss) available per common share - diluted (in dollars per share)	$ 0.21	$ (0.18)	$ (7.38)	$ (0.48)