Reportable Segment (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2020 USD ($) segment	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Business segments
Number of business segments | segment									1
Revenues	$ 40,990	$ 43,727	$ 37,547	$ 38,440	$ 37,965	$ 43,559	$ 38,954	$ 37,799	$ 160,704	$ 158,277	$ 144,435
Depreciation, depletion and amortization									19,379	17,394	17,391
Gross profit (loss)	13,171	14,182	10,357	9,877	9,773	13,483	9,727	8,693	47,587	41,676	30,486
Operating profit									33,869	29,246	20,002
Assets	279,098				247,037				279,098	247,037	244,671
Capital expenditures									17,133	27,100	53,762
Impairment of long-lived assets									1,550	930
Unallocated corporate assets and cash items
Business segments
Assets	88,152				61,380				88,152	61,380	75,489
Lime and limestone operations
Business segments
Depreciation, depletion and amortization									18,664	16,432	16,741
Gross profit (loss)									47,983	42,043	29,482
Operating profit									35,815	30,543	18,998
Assets	190,946				185,657				190,946	185,657	169,182
Capital expenditures									17,133	27,100	53,762
Other
Business segments
Depreciation, depletion and amortization									715	962	650
Gross profit (loss)									(396)	(367)	1,004
Operating profit									(1,946)	(1,297)	1,004
Lime and limestone operations
Business segments
Revenues	40,658	43,473	37,362	38,214	37,670	43,265	38,581	37,465
Lime and limestone operations | Lime and limestone operations
Business segments
Revenues									159,707	156,981	141,922
Other
Business segments
Revenues	$ 332	$ 254	$ 185	$ 226	$ 295	$ 294	$ 373	$ 334
Other | Other
Business segments
Revenues									$ 997	$ 1,296	$ 2,513