Income Taxes - Sources of Temporary Differences (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax liabilities:
Fixed assets	$ (27,374)	$ (23,805)
Operating lease right-of-use assets	(2,223)	(2,475)
Other	(72)	(84)
State deferred taxes	(3,210)	(3,405)
Total deferred tax liabilities	(32,879)	(29,769)
Deferred tax assets:
Captive insurance subsidiary	378	312
Accrued liabilities	2,325	2,006
Stock compensation	2,635	2,118
Operating lease liabilities	2,232	2,478
SmartStop TRS	219	219
Other	1,554	50
State deferred taxes	6,725	7,250
Total deferred tax assets	16,068	14,433
Valuation allowance	(3,302)	(3,665)
Net deferred income tax liabilities	$ (20,113)	$ (19,001)