Commitments and Contingencies (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2015	Dec. 31, 2011	Dec. 31, 2014	Sep. 30, 1999
Commitments and Contingencies
Provision for contingent obligation	$ (125,000)	$ 70,000	$ (102,000)	$ (8,000)
Provision for contingent obligation	1,711,000		1,711,000				$ 1,813,000
Indirect Guarantee of Indebtedness
Commitments and Contingencies
Balance available in the sales and incremental property tax fund	2,910,000		2,910,000				$ 1,932,000
Amount paid into the sales and incremental property tax fund			983,000
Indirect Guarantee of Indebtedness | Scenario Forecast
Commitments and Contingencies
Deduction from the sales and incremental property tax fund for principal and interest payments					$ 810,000
Nontaxable Municipal Bonds | Indirect Guarantee of Indebtedness
Commitments and Contingencies
Aggregate principal amount								$ 25,900,000
Outstanding amount of debt	18,000,000		18,000,000
Irrevocable direct-pay letter of credit issued	18,302,000		18,302,000
Nontaxable Municipal Bonds | Minimum | Indirect Guarantee of Indebtedness
Commitments and Contingencies
Annual principal payments	800,000		800,000
Nontaxable Municipal Bonds | Maximum | Indirect Guarantee of Indebtedness
Commitments and Contingencies
Annual principal payments	1,600,000		1,600,000
Nashville Superspeedway | Nontaxable Municipal Bonds
Commitments and Contingencies
Provision for contingent obligation						$ 2,250,000
(Decreased) increased in the provision for contingent obligation due to changing interest rates	(125,000)	$ 70,000	(102,000)	$ (8,000)
Provision for contingent obligation	$ 1,711,000		$ 1,711,000