Consolidated Statements of Other Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Net loss after taxes/net decrease on net assets resulting from operations	$ (13,884)
Bank Holding Company Accounting [Member]
Net loss after taxes/net decrease on net assets resulting from operations	(13,884)
Other comprehensive loss, net of tax	(255)
Total comprehensive loss	(14,139)
Less: comprehensive income attributable to the noncontrolling interest	763
Total comprehensive loss attributable to Medallion Financial Corp.	$ (14,902)
Investment Company Accounting [Member]
Net loss after taxes/net decrease on net assets resulting from operations		$ (14,874)	$ (4,797)		$ (3,686)
Total comprehensive loss		(14,874)	(4,797)		(3,686)
Total comprehensive loss attributable to Medallion Financial Corp.		$ (14,874)	$ (4,797)		$ (3,686)
Bank Holding Company and Investment Company [Member]
Net loss after taxes/net decrease on net assets resulting from operations				$ (28,758)
Other comprehensive loss, net of tax				(255)
Total comprehensive loss				(29,013)
Less: comprehensive income attributable to the noncontrolling interest				763
Total comprehensive loss attributable to Medallion Financial Corp.				$ (29,776)