Business Operations - Assets held for sale (Details) - Nashville Superspeedway	Mar. 02, 2018 USD ($)	Sep. 01, 2017 USD ($) a	Mar. 31, 2018 USD ($) a	Feb. 09, 2018 USD ($) a	Dec. 31, 2017 USD ($) a	Aug. 17, 2017 USD ($) a
Assets held for sale | Long term assets
Business Operations.
Nashville Superspeedway facility			$ 23,567,000		$ 23,545,000
147 Acres of Property
Business Operations.
Number of acres of property | a						147
Purchase price per acre						$ 35,000
Proceeds, less closing costs	$ 4,945,000
Net proceeds after taxes	$ 4,150,000
147 Acres of Property | Assets held for sale
Business Operations.
Number of acres of property | a					147
Nashville Superspeedway facility					$ 2,455,000
Additional 88.03 Acres of Property
Business Operations.
Number of acres of property | a		88.03
Purchase price per acre		$ 55,000
Period of option to execute the agreement		3 years
Additional 86.45 Acres of Property
Business Operations.
Number of acres of property | a				86.45
Purchase price per acre				$ 66,685
Additional 50.51 Acres of Property
Business Operations.
Number of acres of property | a				50.51
Purchase price per acre				$ 35,000
Total 224.99 Acres of Property
Business Operations.
Number of acres of property | a				224.99
Purchase price per acre				$ 12,374,000
1000 Acres of Remaining Property | Minimum | Assets held for sale
Business Operations.
Number of acres of property | a			1,000