Funds Borrowed - Summary of Key Attributes of Various Borrowing Arrangements with Lenders (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
Notes Payable [Line Items]
Average Interest Rate	2.59%	[1]
Notes Payable to Banks [Member]
Notes Payable [Line Items]
Note Amounts	$ 76,925
Balance outstanding	$ 72,715
Average Interest Rate	4.19%	[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	Jul. 30, 2018
Maturity Dates	Aug. 31, 2019
Type	Term loans and demand notes secured by pledged loans	[2]
Note Amounts	$ 51,217
Balance outstanding	$ 51,217
Monthly Payment	Interest	[3]
Average Interest Rate	4.54%
Notes Payable to Banks [Member] | Medallion Chicago [Member]
Notes Payable [Line Items]
Note Dates	Nov. 30, 2011
Note Dates	Dec. 31, 2011
Maturity Dates	Oct. 31, 2016
Maturity Dates	Jun. 30, 2019
Type	Term loans secured by owned Chicago medallions	[4]
Note Amounts	$ 25,708
Balance outstanding	$ 21,498
Monthly Payment	$181 principal & interest
Average Interest Rate	3.34%

[1] Weighted average contractual rate as of June 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 3.75%, one note has an interest rate of LIBOR plus 3.75%, 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] $12,708 guaranteed by the Company.