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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, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Affiliate Equity [Abstract]
Net income (controlling interest)	$ 124.9	$ 125.4	$ 394.9	$ 374.2
Decrease in controlling interest paid-in capital from Affiliate equity issuances	(0.5)	(0.3)	(3.8)	(0.6)
Decrease in controlling interest paid-in capital from Affiliate equity repurchases	(31.7)	(12.7)	(63.8)	(81.8)
Net income (controlling interest) including the net impact of Affiliate equity transactions	$ 92.7	$ 112.4	$ 327.3	$ 291.8

X

- Definition

The increase (decrease) in additional paid-in capital of the reporting entity from purchases and sales of Affiliate equity.

+ References

No definition available.

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- Definition

Adjustments to Additional Paid in Capital Decrease in Carrying Amount of Redeemable Noncontrolling Interests

+ References

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- Definition

Affiliate Equity [Abstract]

+ References

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X

- Definition

Increase (decrease) in equity during the period due to net income attributable to the parent company and net transfers with non-controlling interests.

+ References

No definition available.

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X

- Definition

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

+ References

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