COMMON EQUITY - ADOPTION OF ASU 2016-09 (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Changes in retained earnings [Roll Forward]
Balance at December 31, 2016			$ 4,613.9
Net income attributed to common shareholders	$ 215.4	$ 217.0	771.1	$ 744.6
Common stock dividends			(492.4)
Cumulative effect of adoption of ASU 2016-09	15.7		15.7
Balance at September 30, 2017	$ 4,908.3		$ 4,908.3

Amount of paid and unpaid common stock dividends declared with the form of settlement in cash.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

+ References

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Amount of cumulative effect of the change in accounting principle or new accounting pronouncement on retained earnings or other components of equity or net assets in the statement of financial position as of the beginning of the earliest period presented.

+ References

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The cumulative amount of the reporting entity's undistributed earnings or deficit.

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