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INCOME TAXES. (Changes in Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] |  |  |
Balance at beginning of year | $ 6.2 | $ 5.8 | $ 5.6
Changes in tax positions related to current year | 1.5 | 0.6 | 0.7
Changes in tax positions related to prior years | 0.1 | 0.0 | 1.8
Changes in tax positions related to expired statute of limitations | (0.2) | (0.2) | (2.3)
Balance at end of year | $ 7.6 | $ 6.2 | $ 5.8

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- Definition Unrecognized Tax Benefits, Increase (Decrease) Resulting from Current Period Tax Positions + References No definition available. + Details
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- Definition Unrecognized Tax Benefits, Increase (Decrease) Resulting from Prior Period Tax Positions + References No definition available. + Details
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
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- Definition Amount of unrecognized tax benefits. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319 + Details
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- Definition Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319 + Details
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