FINANCIAL INSTRUMENTS AND RISK MANAGEMENT (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
Sep. 30, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Aggregate purchase price of guarantees	$ 0.6
Market value an aggregate purchase price of guarantees	0.6
Financing receivable, net	10.9	10.8
Threshold period past due for collection	90 days
Threshold period past due for write-off of financing receivable	12 months
Financing receivable, recorded investment, equal to greater than 90 days past due	0.3	0.4
Allowance for credit losses recognized	0.3	0.4
Natural Gas Distribution
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Number of customers	423,000
Estimate of Fair Value Measurement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	266.4	258.8
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	$ 249.8	$ 249.9

Number of customers, including residential, commercial and insustrial.

No definition available.

Name:	lg_NumberOfCustomers
Namespace Prefix:	lg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Recorded Unconditional Purchase Obligation Market Value

+ References

No definition available.

+ Details

Name:	lg_RecordedUnconditionalPurchaseObligationMarketValue
Namespace Prefix:	lg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Threshold Period Past Due for Collection

+ References

No definition available.

+ Details

Name:	lg_ThresholdPeriodPastDueforCollection
Namespace Prefix:	lg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of direct write-downs of financing receivables charged against the allowance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

-Subparagraph (c)(3)

-URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953423-111524

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Financing receivables that are equal to or greater than 90 days past due.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7A

-URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953401-111524

+ Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

Name:	us-gaap_LongTermDebtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Net amount of the investment in a contractual right to receive money on demand or on fixed or determinable dates that is recognized as an asset in the creditor's statement of financial position. Examples include, but are not limited to, credit card receivables, notes receivable and receivables relating to lessor's rights to payments from leases other than operating leases that have been recorded as assets. Excludes trade accounts receivable with contractual maturity of one year or less and arose from the sale of goods or services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.3)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 3

-Article 5

+ Details

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

- Definition

Amount of the recorded obligation to transfer funds in the future for fixed or minimum amounts or quantities of goods or services at fixed or minimum prices (for example, as in take-or-pay contracts or throughput contracts).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 440

-SubTopic 10

-Section 50

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6394976&loc=d3e25383-109308

+ Details

Name:	us-gaap_RecordedUnconditionalPurchaseObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Threshold period past due for financing receivable to write off as uncollectible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_ThresholdPeriodPastDueForWriteoffOfFinancingReceivable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration