Restructuring Charges (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014
Restructuring Charges [Abstract]
Restructuring Costs	$ 5.7us-gaap_RestructuringCosts
Restructuring Cost, Severance Costs	5.3lxrx_RestructuringCostSeveranceCosts
Other Restructuring Costs	0.4us-gaap_OtherRestructuringCosts
Restructuring and Related Cost, Cost Incurred to Date	5.6
Restructuring and Related Costs, Cost Incurred to Date, Research and Development	4.9
Restructuring and Related Costs, Cost Incurred to Date, General and Administrative	0.7
Restructuring and Related Costs, Cost Incurred to Date, Stock-based Compensation	0.1
Restructuring Reserve	$ 0.3us-gaap_RestructuringReserve

Amount of costs incurred to date for the specified type of restructuring cost in general and administrative expense.

No definition available.

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- Definition

Amount of costs incurred to date for the specified type of restructuring cost in research and development expense.

+ References

No definition available.

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- Definition

Amount of costs incurred to date for restructuring costs as stock-based compensation.

+ References

No definition available.

+ Details

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- Definition

Amount expected to be recognized in earnings for severance costs.

+ References

No definition available.

+ Details

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- Definition

Amount of other expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses associated with a discontinued operation or an asset retirement obligation.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 420

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 420

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SAB TOPIC 5.P.4(b))

-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 420

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 5.P.3)

-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140864-122747

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section P

-Subsection 3, 4

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- Definition

Amount of costs incurred to date for the specified restructuring cost.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 420

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 420

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SAB TOPIC 5.P.4(b))

-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747

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-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section P

-Subsection 3, 4

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- Definition

Amount, after cash payment, of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

+ References

+ Details

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- Definition

Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 420

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SAB TOPIC 5.P.4(b))

-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747

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

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section P

-Subsection 3, 4

+ Details

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