Income Taxes - Sources of Temporary Differences (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax liabilities:
Fixed assets	$ (23,805)	$ (20,907)
Operating lease right-of-use assets	(2,475)	0
Other	(84)	(96)
State deferred taxes	(3,405)	(3,076)
Total deferred tax liabilities	(29,769)	(24,079)
Deferred tax assets:
Captive insurance subsidiary	312	324
Accrued liabilities	2,006	1,772
Stock compensation	2,118	1,604
Operating lease liabilities	2,478	0
SmartStop TRS	219	219
Other	50	53
State deferred taxes	7,250	7,196
Total deferred tax assets	14,433	11,168
Valuation allowance	(3,665)	(3,872)
Net deferred income tax liabilities	$ (19,001)	$ (16,783)