REPURCHASES OF COMMON STOCK (Details) - Common Class A [Member] - USD ($) shares in Millions, $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jul. 31, 2018
Repurchases of Common Stock [Abstract]
Common stock repurchased (in shares)	0.2	0.4	0.6	0.8
Common stock repurchased	$ 12.4	$ 25.7	$ 48.2	$ 47.8
Authorized amount for repurchase program					$ 500.0
Available for repurchase under the repurchase program	$ 492.4		$ 492.4

Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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