Asset Retirement Obligations - Additional Information (Detail) $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
Asset Retirement Obligation Disclosure [Abstract]
Financial assurance in form of surety bond	$ 28.2
Asset retirement obligation liabilities expected, present value	$ 26.9

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