Income Taxes - Differences in Statutory Rate and Effective Rate (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
U.S. statutory rate			$ 10,405	$ 13,873	$ 9,903
Permanent items			505	(1,916)	(570)
Write-off of foreign tax and research credits			0	0	7,125
Foreign tax credits			0	0	(319)
Uncertain tax positions			3,227	3,128	1,529
Other tax credits			(742)	(175)	90
State and local taxes			2,125	1,252	433
Impact of rate change on deferred taxes		$ 45,100	0	45,129	(383)
True-up of prior year tax			0	7	(2,751)
Foreign tax rate differential			30	97	(242)
Valuation allowance			(4,073)	(141,094)	(13,292)
Benefit of windfall related to stock compensation			(1,760)	(2,723)	0
Increase in indemnification deferred tax asset			(731)	(1,055)	0
Other			44	(269)	9
Income tax expense (benefit)	$ 4,000		$ 9,030	$ (83,746)	$ 1,532

Effective Income Tax Rate Reconciliation, Increase In Indemnification Deferred Tax Asset

No definition available.

Name:	lnth_EffectiveIncomeTaxRateReconciliationIncreaseInIndemnificationDeferredTaxAsset
Namespace Prefix:	lnth_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to foreign tax credit.

+ References

No definition available.