Summary of Significant Accounting Policies - Summary of Purchase Price Accounting (Detail) - USD ($) $ in Thousands		Dec. 31, 2018	Apr. 02, 2018	Mar. 31, 2018	Dec. 31, 2017
Assets
Cash					$ 110,233
Net loans		$ 981,487
Other assets					58,827
Liabilities
Other liabilities					$ (3,836)
Intangibles assets		53,982
Intellectual Property [Member]
Liabilities
Intangibles assets		21,176
Contractor Relationships [Member]
Liabilities
Intangibles assets		6,641
Race Organization [Member]
Liabilities
Intangibles assets		26,165
Medallion Bank [Member]
Assets
Cash		$ 100
Net loans	[1]		$ 890,000
Other assets			130,393
Liabilities
Funds borrowed and other liabilities			(853,650)
Total fair value excluding goodwill and intangibles			166,743
Goodwill			150,803
Intangibles assets			28,900
Total fair value	[2]		346,446	$ 346,446
RPAC [Member] | Operating Segments [Member]
Assets
Cash			1,647
Race cars held for sale			916
Other assets			1,902
Liabilities
Deferred revenue			(6,531)
Notes payable	[3]		(27,220)
Other liabilities			(2,275)
Total fair value excluding goodwill and intangibles			(30,584)
Intangibles assets	[4]		31,779
Total fair value	[5]		1,195	$ 1,195
RPAC [Member] | Operating Segments [Member] | Fixed Assets Net [Member]
Assets
Net fixed assets			774
RPAC [Member] | Operating Segments [Member] | Race Cars and Parts Net [Member]
Assets
Net fixed assets			$ 203

[1] Includes $12,387 of premiums associated with the loan portfolio.

[2] Includes $26,303 of preferred stock held by the U.S. Treasury. See Note 21 for details.

[3] Includes $20,177 due to the Company and its affiliates as of March 31, 2018.

[4] As of December 31, 2018 an assessment of the intangible asset resulted in impairment of $5,615 based upon the analysis of current market conditions using discounted cash flows.

[5] Fair value as of March 31, 2018 represents the Company's investment in RPAC series D units.