BUSINESS COMBINATION - PROFORMA (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Pro-forma Combined
Operating revenue	$ 512.5	$ 483.0	$ 986.9	$ 949.5
Net income	$ 24.0	$ 19.9	$ 31.0	$ 38.7
Basic Earnings Per Share (in dollars per share)	$ 0.56	$ 0.46	$ 0.72	$ 0.89
Diluted Earnings Per Share (in dollars per share)	$ 0.55	$ 0.46	$ 0.72	$ 0.89
Weighted Average Number of Shares Outstanding:
Basic	43.1	43.1	43.1	43.3
Diluted	43.3	43.4	43.3	43.7

The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)-(3)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

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Amount after tax of pro forma income from continuing operations as if the business combination had been completed at the beginning of a period.

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The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

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