Loans and Allowance for Loan Losses - Summary of Activity in Allowance for Loan Losses (Parenthetical) (Detail) $ in Thousands	Jun. 30, 2018 USD ($)
Financing Receivable, Allowance for Credit Losses [Line Items]
Unallocated allowance	$ 21,425
Medallion Bank [Member] \| Financing Receivables, 90 Days Past Due [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Unallocated allowance	$ 6,663

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-SubTopic 210
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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Name:	us-gaap_LoansAndLeasesReceivableAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant