Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)		3 Months Ended		12 Months Ended
	Apr. 02, 2018	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Aug. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Non-marketable securities		$ 10,341,000		$ 10,079,000
Investment securities Amortized to interest income		55,000	$ 12,000
Net loan origination costs		18,379,000		17,839,000
Net amortization to income		1,304,000	1,151,000
Premiums in loan portfolio		$ 71,695,000		60,413,000
Percentage of write down of loan balance		40.00%
Loans pledged as collateral		$ 24,881,000		28,833,000
Principal portion of loans serviced, fair value		108,515,000		113,581,000
Bank's reserves against future losses	$ 17,351,000
General reserve benefit	7,266,000	$ 7,266,000
Intangible assets useful life		20 years
Goodwill		$ 150,803,000	150,803,000	150,803,000
Intangible assets, net		52,175,000	53,620,000	52,536,000
Amortization of intangible assets		361,000	361,000
Financing receivable, recorded investment, 90 days past due and still accruing		0		0
Depreciation and amortization		121,000	100,000
Amortization expense		723,000	520,000
Deferred costs		$ 4,674,000	$ 4,411,000	$ 5,105,000
Potential dilutive common shares excluded from EPS computation		807,368	471,000
Stock based compensation award		335,773	374,377
Stock based compensation award, Amount		$ 466,000	$ 165,000
Stock based compensation award per diluted common share		$ 0.02	$ 0.01
Unrecognized compensation cost related to unvested stock options and restricted stock		$ 3,369,000
Unrecognized compensation cost related to unvested stock options and restricted stock, recognition period		48 months
Tier 1 leverage capital ratio		18.78%
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	163,098	216,148
Restricted Stock Units [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stock based compensation award		0	0	26,040
Minimum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful life of fixed assets		3 years
Tier 1 leverage capital to total assets ratio		15.00%
Maximum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful life of fixed assets		10 years
Medallion Bank [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reserves against future losses		$ 2,469,000
Amortization of intangible assets				$ 0
Additional impairment of goodwill		0
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		5,429,000	$ 7,956,000	5,758,000
Loan portfolio premium amortized to interest income		329,000	1,092,000
Additional impairment of intangible assets		0
91+ [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Premiums in loan portfolio		7,014,000		8,663,000
91+ [Member] | Loans [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Premiums in loan portfolio		$ 7,014,000		$ 8,663,000
Total loans more than 90 days past due ,percentage		0.60%		0.76%
Bank Holding Company Accounting [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net premium on investment securities		$ 252,000		$ 248,000
Private Placement [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Interest reserve			$ 2,970,000		$ 2,970,000