Income Taxes - Sources of Temporary Differences (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Liabilities, Gross [Abstract]
Fixed assets	$ (20,907)	$ (15,271)
Other	(96)	(108)
State deferred taxes	(3,076)	(2,822)
Total deferred tax liabilities	(24,079)	(18,201)
Deferred Tax Assets, Gross [Abstract]
Captive insurance subsidiary	324	252
Accrued liabilities	1,772	873
Stock compensation	1,604	1,287
Solar credit	0	43
Other	53	57
SmartStop TRS	219	219
State deferred taxes	7,196	7,802
Total deferred tax assets	11,168	10,533
Valuation allowance	(3,872)	(4,924)
Net deferred income tax liabilities	$ (16,783)	$ (12,592)