Commitments and Contingencies (Details 4) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2013
Changes in the accrued product quality issue
Total accrued product quality issue, beginning balance	$ 6.7
Changes in estimates associated with pre-existing liabilities	0
Product quality claims	(0.6)
Total accrued product quality issue, ending balance	$ 6.1

Product Quality Issue Accrual, Changes in estimates associated with pre-existing liabilities

No definition available.

Name:	lii_ProductQualityIssueAccrualChangesInEstimatesAssociatedWithPreExistingLiabilities
Namespace Prefix:	lii_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration