SIGNIFICANT ACCOUNTING POLICIES - Schedule of Changes in the Carrying Amount of Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 102.3	$ 102.3
Changes to goodwill	0.0	0.0
Goodwill, ending balance	102.3	102.3
Materials & Construction
Goodwill [Roll Forward]
Goodwill, beginning balance	93.6	93.6
Changes to goodwill	0.0	0.0
Goodwill, ending balance	93.6	93.6
Commercial Real Estate
Goodwill [Roll Forward]
Goodwill, beginning balance	8.7	8.7
Changes to goodwill	0.0	0.0
Goodwill, ending balance	$ 8.7	$ 8.7

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=64834752&loc=SL49117168-202975

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant