Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Aug. 31, 2019	Mar. 31, 2019	Apr. 02, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Interest-bearing funds deposited in other banks	$ 2,500,000			$ 2,500,000
Non-marketable securities	10,284,000			10,284,000		$ 10,079,000
Investment securities Amortized to interest income	85,000		$ 21,000	219,000	$ 46,000
Net loan origination costs				20,806,000		17,839,000
Net amortization to income	1,681,000		1,364,000	4,572,000	3,753,000
Premiums in loan portfolio	109,076,000			$ 109,076,000		60,413,000
Percentage of write down of loan balance				40.00%
Loans pledged as collateral	18,908,000			$ 18,908,000		28,833,000
Principal portion of loans serviced, fair value	107,809,000			107,809,000		113,581,000
Loans write down to collateral value	19,686,000		9,209,000	$ 38,894,000	39,248,000
Intangible assets useful life				20 years
Goodwill	150,803,000		150,803,000	$ 150,803,000	150,803,000	150,803,000
Intangible assets, net	51,452,000		52,898,000	51,452,000	52,898,000	52,536,000
Amortization of intangible assets	362,000		361,000	1,084,000	1,084,000
Financing receivable, recorded investment, 90 days past due and still accruing	0			0		0
Depreciation and amortization	142,000		109,000	403,000	313,000
Amortization expense	648,000		613,000	1,957,000	1,731,000
Deferred costs	4,795,000		5,589,000	$ 4,795,000	$ 5,589,000	$ 5,105,000
Potential dilutive common shares excluded from EPS computation				834,684	468,055
Stock based compensation award				335,773	375,481
Stock based compensation award, Amount	$ 508,000		$ 348,000	$ 1,495,000	$ 853,000
Stock based compensation award per diluted common share	$ 0.02		$ 0.01	$ 0.06	$ 0.03
Unrecognized compensation cost related to unvested stock options and restricted stock	$ 2,484,000			$ 2,484,000
Unrecognized compensation cost related to unvested stock options and restricted stock, recognition period				42 months
Tier 1 leverage capital ratio	15.47%			15.47%
Capital conversation buffer				2.50%		2.50%
Restricted Shares [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stock based compensation award		165,674		165,674	178,266	216,148
Restricted Stock Units [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stock based compensation award				47,156	26,040
RPAC [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Premiums in loan portfolio									$ 12,387,000
Financing receivable, recorded investment, 90 days past due and still accruing	$ 4,358,000		$ 6,161,000	$ 4,358,000	$ 6,161,000	$ 5,758,000
Loan portfolio premium amortized to interest income	893,000		$ 713,000	1,401,000	$ 2,886,000
Additional impairment of intangible assets				0
Medallion Bank [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Amortization of intangible assets						0
Additional impairment of goodwill				0
New York City [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans write down to collateral value				$ 90,300,000
Increase in provision for loan losses	$ 24,749,000,000
CARES Act [Member] | Consumer Portfolio [Member] | Consumer Loans [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Percentage of consumer loans placed on deferment	95.00%			95.00%
91+ [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Premiums in loan portfolio	$ 13,403,000			$ 13,403,000		8,663,000
91+ [Member] | Loans [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Premiums in loan portfolio	$ 13,402,000			$ 13,402,000		$ 8,663,000
Total loans more than 90 days past due ,percentage	1.07%			1.07%		0.76%
Bank Holding Company Accounting [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net premium on investment securities				$ 298,000		$ 248,000
Private Placement [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Interest reserve							$ 2,970,000	$ 2,970,000
Minimum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Interest bearing loan term				4 years
Estimated useful life of fixed assets				3 years
Tier 1 leverage capital to total assets ratio	15.00%			15.00%
Maximum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Interest bearing loan term				7 years
Estimated useful life of fixed assets				10 years