Organization and Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended	6 Months Ended
	Mar. 31, 2010 USD ($)	Jun. 30, 2024 SONGS
Organization And Summary Of Significant Accounting Policies [Line Items]
Date of formation of Mills Music Trust		Dec. 03, 1964
Minimum payment of quarterly Contingent Portion | $	$ 167,500
Top 50 Songs in the Catalogue		EMI has provided the Trust with a listing of the top 50 earning songs in the Catalogue during the 2023 calendar year (the “Top 50 Songs”), together with certain copyright information with respect to each of the Top 50 Songs (the “Listing”). A copy of the Listing, as provided by EMI, is included in the Trust’s annual report on Form 10-K for the fiscal year ended December 31, 2023. The Listing does not include any information regarding Copyrighted Songs for the 2024 calendar year.
Minimum [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Percentage of Contingent Portion of gross royalty income	65.00%
Maximum [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Percentage of Contingent Portion of gross royalty income	75.00%
Top 50 Song Listing [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Estimated number of songs in the Catalogue		12,000
Estimated number of songs producing royalty income		1,430
Top 50 Song Listing		50