Income Taxes - Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax [Line Items]
U.S. federal, Current	$ 4,174	$ 9,518	$ 7,686
State and local, Current	2,706	2,681	1,746
Foreign, Current	1,546	1,500	1,527
Total Current	8,426	13,699	10,959
U.S. federal, Deferred	359	(935)	(930)
State and local, Deferred	(170)	(6)	(246)
Foreign, Deferred	615	598	12,275
Total, Deferred	804	(343)	11,099
U.S. federal, Total	4,533	8,583	6,756
State and local, Total	2,536	2,675	1,500
Foreign, Total	2,161	2,098	13,802
Income tax expense	9,230	13,356	22,058
LAMAR MEDIA CORP. AND SUBSIDIARIES [Member]
Income Tax [Line Items]
U.S. federal, Current	4,174	9,518	7,686
State and local, Current	2,706	2,681	1,746
Foreign, Current	1,546	1,500	1,527
Total Current	8,426	13,699	10,959
U.S. federal, Deferred	359	(935)	(930)
State and local, Deferred	(170)	(6)	(246)
Foreign, Deferred	615	598	12,275
Total, Deferred	804	(343)	11,099
U.S. federal, Total	4,533	8,583	6,756
State and local, Total	2,536	2,675	1,500
Foreign, Total	2,161	2,098	13,802
Income tax expense	$ 9,230	$ 13,356	$ 22,058