Non-cash Financing Activities - Additional Information (Detail) - USD ($)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Supplemental Cash Flow Elements [Abstract]
Non cash financing activities related to financing lease liabilities	$ 19,891,000
Non-cash financing activity		$ 0	$ 0

Transaction affecting assets or liabilities which did not result in cash receipts or payments during the period.

No definition available.

Name:	lamr_NonCashFinancingTransaction
Namespace Prefix:	lamr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration