Asset Retirement Obligations - Additional Information (Detail) $ in Millions	9 Months Ended
Sep. 30, 2015 USD ($)
Asset Retirement Obligation Disclosure [Abstract]
Financial assurance in form of surety bond	$ 28.2
Unfunded standby letter of credit	8.8
Asset retirement obligation liabilities expected, present value	$ 26.0

Represents the amount of expected present value of asset retirement obligations.

No definition available.

Name:	lnth_AssetRetirementObligationLiabilitiesExpectedPresentValue
Namespace Prefix:	lnth_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant