Label	Element	Value
No Load Class \| Grayscale Bitcoin Trust ETF [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	22.90%
No Load Class \| Texas Pacific Land Corp. [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	19.20%
No Load Class \| White Mountains Insurance Group Ltd. [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	4.10%
No Load Class \| Landbridge Co. LLC [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	4.00%
No Load Class \| Grayscale Bitcoin Mini Trust ETF [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	2.60%
No Load Class \| IG Port, Inc. [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	1.90%
No Load Class \| Galaxy Digital Holdings Ltd. [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	1.50%
No Load Class \| GAMCO Investors, Inc. [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	1.30%
No Load Class \| Wheaton Precious Metals Corp. [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	1.20%
No Load Class \| Mesabi Trust [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	1.20%
No Load Class \| Finance and Insurance [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	31.70%
No Load Class \| Mining, Quarrying, and Oil and Gas Extraction [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	26.60%
No Load Class \| Management of Companies and Enterprises [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	7.00%
No Load Class \| Entertainment [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	1.90%
No Load Class \| Real Estate and Rental and Leasing [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	1.20%
No Load Class \| Transportation and Warehousing [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	1.20%
No Load Class \| Professional, Scientific, and Technical Services [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	0.60%
No Load Class \| Media [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	0.50%
No Load Class \| Real Estate [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	0.30%
No Load Class \| Accommodation and Food Services [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	0.20%
No Load Class \| United States
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	61.70%
No Load Class \| Canada
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	5.70%
No Load Class \| Japan
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	2.50%
No Load Class \| United Kingdom
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	1.00%
No Load Class \| Sweden
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	0.50%
No Load Class \| Germany
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	0.30%
No Load Class \| Cayman Islands
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	0.30%
No Load Class \| Netherlands
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	0.30%
No Load Class \| Brazil
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	0.10%
No Load Class \| Greece
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Net Asset Value	oef_PctOfNav	0.10%