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Company's Liability for Environmental Obligations (Detail) - USD ($) $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2015 | Dec. 31, 2014
Environmental Exit Cost [Line Items] |  |  |  |
Total Balance at Beginning of period | $ 5.5 | $ 14.8 |  |
Additions | 2.9 | 1.3 |  |
Less: Payments / Reductions | 5.6 | 10.6 |  |
Total Balance at End of period | 2.8 | 5.5 |  |
Less: Current Portion |  |  | $ 1.3 | $ 3.5
Noncurrent Balance |  |  | 1.5 | 2.0
Total Balance at End of period | 5.5 | 14.8 | 2.8 | 5.5
Fitchburg Gas and Electric Light Company |  |  |  |
Environmental Exit Cost [Line Items] |  |  |  |
Total Balance at Beginning of period | 1.9 | 12.0 |  |
Less: Payments / Reductions | 0.7 | 10.1 |  |
Total Balance at End of period | 1.2 | 1.9 |  |
Less: Current Portion |  |  | 0.2 | 1.9
Noncurrent Balance |  |  | 1.0 |
Total Balance at End of period | 1.9 | 12.0 | 1.2 | 1.9
Northern Utilities Inc |  |  |  |
Environmental Exit Cost [Line Items] |  |  |  |
Total Balance at Beginning of period | 3.6 | 2.8 |  |
Additions | 2.9 | 1.3 |  |
Less: Payments / Reductions | 4.9 | 0.5 |  |
Total Balance at End of period | 1.6 | 3.6 |  |
Less: Current Portion |  |  | 1.1 | 1.6
Noncurrent Balance |  |  | 0.5 | 2.0
Total Balance at End of period | $ 3.6 | $ 2.8 | $ 1.6 | $ 3.6

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- Definition Total costs accrued as of the balance sheet date for environmental loss contingencies. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 25 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6395460&loc=d3e13647-108346 + Details
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- Definition The aggregate amount disbursed during the reporting period to settle environmental loss contingencies. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 5.Y.Q2) -URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751 + Details
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- Definition The amount added to the accrual for newly incurred environmental loss contingencies. These additions include remediation expense and interest accretion. These additions do not relate to changes in the environmental accrual related to a business acquisition or divestiture, to currency movements, or revisions in previously existing estimates. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 5.Y.Q2) -URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751 + Details
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