Funds Borrowed - Summary of Key Attributes of Various Borrowing Arrangements with Lenders (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($)
Notes Payable [Line Items]
Average Interest Rate	2.64%	[1]
Notes Payable to Banks [Member]
Notes Payable [Line Items]
Note Amounts	$ 73,329
Balance outstanding	$ 67,304
Average Interest Rate	4.47%	[1]
Notes Payable to Banks [Member] | Parent Company [Member]
Notes Payable [Line Items]
Note Dates	Apr. 30, 2011
Note Dates	Aug. 31, 2014
Maturity Dates	Nov. 30, 2018
Maturity Dates	Jul. 31, 2019
Type	Term loans and demand notes secured by pledged loans	[2]
Note Amounts	$ 47,621
Balance outstanding	$ 47,621
Monthly Payment	Interest	[3]
Average Interest Rate	4.87%
Notes Payable to Banks [Member] | Parent Company [Member] | Prime Rate [Member]
Notes Payable [Line Items]
Debt Instrument interest rate, stated percentage	5.25%
Notes Payable to Banks [Member] | Medallion Chicago [Member]
Notes Payable [Line Items]
Note Dates	Nov. 30, 2011
Note Dates	Dec. 31, 2011
Maturity Dates	Jun. 30, 2019
Maturity Dates	Jun. 30, 2021
Type	Term loans secured by owned Chicago medallions	[4]
Note Amounts	$ 25,708
Balance outstanding	$ 19,683
Monthly Payment	171 principal & interest
Average Interest Rate	3.50%
Debt Instrument interest rate, stated percentage	3.50%

[1] Weighted average contractual rate as of September 30, 2018.

[2] One note has an interest rate of Prime, one note has an interest rate of Prime plus 0.50%, one note has a fixed interest rate of 4.50%, one note has an interest rate of LIBOR plus 3.50%, and the other interest rates on these borrowings are LIBOR plus 2%.

[3] Various agreements call for remittance of all principal received on pledged loans subject to minimum monthly payments ranging from $0 to $75.

[4] Guaranteed by the Company.