COMMON EQUITY - ADOPTION OF ASU 2016-09 (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Changes in retained earnings [Roll Forward]
Balance at December 31, 2016	$ 4,613.9
Net income attributed to common shareholders	356.6	$ 346.2
Common stock dividends	(164.1)
Cumulative effect of adoption of ASU 2016-09	15.7
Other	(0.1)
Balance at March 31, 2017	$ 4,822.0

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

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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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Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period).

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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.

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

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This element represents movements included in the statement of changes in stockholders' equity which are not separately disclosed or provided for elsewhere in the taxonomy.

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