Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenues									$ 104,778	$ 111,081	$ 147,998
Gross profit	$ 5,289	$ 2,475	$ 4,597	$ 4,558	$ 2,230	$ 1,647	$ 2,237	$ 5,968	16,919	12,082	(11,232)
Earnings of unconsolidated mines	16,734	16,197	13,475	14,955	14,453	15,102	13,035	12,648	61,361	55,238	48,432
Operating profit (loss)	6,506	6,989	9,513	9,806	(707)	(12,779)	3,526	8,301	32,814	(1,659)	(3,727)
Income from continuing operations									28,463	2,956	2,273
Income from discontinued operations									1,874	26,651	19,711
Net income	$ 10,172	$ 8,398	$ 6,789	$ 4,978	$ 24,131	$ (441)	$ 3,115	$ 2,802	$ 30,337	$ 29,607	$ 21,984
Basic earnings (loss) per share:
Continuing operations (USD per share)	$ 1.41	$ 0.49	$ 1.06	$ 1.21	$ (0.68)	$ (0.31)	$ 0.28	$ 1.13	$ 4.17	$ 0.43	$ 0.32
Discontinued operations (USD per share)	0.07	0.74	(0.06)	(0.48)	4.24	0.25	0.17	(0.72)	0.27	3.91	2.82
Basic earnings per share (USD per share)	1.48	1.23	1.00	0.73	3.56	(0.06)	0.45	0.41	4.44	4.34	3.14
Diluted earnings (loss) per share:
Continuing operations (USD per share)	1.40	0.49	1.06	1.20	(0.68)	(0.31)	0.28	1.13	4.14	0.43	0.32
Discontinued operations (USD per share)	0.07	0.74	(0.06)	(0.47)	4.21	0.25	0.17	(0.72)	0.27	3.89	2.81
Diluted earnings per share (USD per share)	$ 1.47	$ 1.23	$ 1.00	$ 0.73	$ 3.53	$ (0.06)	$ 0.45	$ 0.41	$ 4.41	$ 4.32	$ 3.13
NACoal
Diluted earnings (loss) per share:
Legal matter resolution charge					$ 3,300
Operating Segments | NACoal
Segment Reporting Information [Line Items]
Revenues	$ 26,437	$ 21,941	$ 28,100	$ 28,300	25,303	$ 32,402	$ 23,089	$ 30,287	$ 104,778	$ 111,081	$ 147,998
Gross profit									17,198	12,341	(10,816)
Operating profit (loss)	8,550	8,925	10,876	11,326	1,966	(10,912)	4,823	9,742	39,677	5,619	521
Income from continuing operations	9,679	3,331	7,233	8,220	(4,616)	(2,132)	1,944	7,760
NACCO and Other | NACCO and Other
Segment Reporting Information [Line Items]
Gross profit									(279)	(259)	(416)
Operating profit (loss)	(2,044)	(1,936)	(1,363)	(1,520)	(2,673)	(1,867)	(1,297)	(1,441)	(6,863)	(7,278)	$ (4,248)
Income from discontinued operations	$ 493	$ 5,067	$ (444)	$ (3,242)	$ 28,747	1,691	$ 1,171	$ (4,958)
Centennial
Diluted earnings (loss) per share:
Asset impairment						$ 17,400			$ 1,000	$ 17,400