Affiliate Equity - Changes in the Company's Interest in its Affiliates on the Controlling Interest's Equity (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Affiliate Equity [Abstract]
Net income (loss) (controlling interest)	$ 86.3	$ 124.9	$ (6.8)	$ 394.9
Decrease in controlling interest paid-in capital from Affiliate equity issuances	(1.9)	(0.5)	(2.8)	(3.8)
Decrease in controlling interest paid-in capital from Affiliate equity repurchases	(7.6)	(31.7)	(38.2)	(63.8)
Net income (loss) (controlling interest) including the net impact of Affiliate equity transactions	$ 76.8	$ 92.7	$ (47.8)	$ 327.3

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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