Loans and Allowance for Loan Losses - Summary of Activity in Allowance for Loan Losses (Detail) $ in Thousands	3 Months Ended
	Jun. 30, 2018 USD ($)
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for loan losses	$ 30,576
Allowance for loan losses - ending balance	21,425
Recreation [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - ending balance	1,963
Home Improvement [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - ending balance	555
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - ending balance	175
Medallion [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - ending balance	18,732
Bank Holding Company Accounting [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total charge- offs	(11,487)
Total recoveries	2,336
Net charge offs	(9,151)
Provision for loan losses	30,576	[1]
Allowance for loan losses - ending balance	21,425
Bank Holding Company Accounting [Member] | Recreation [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total charge- offs	(4,646)
Total recoveries	1,899
Bank Holding Company Accounting [Member] | Home Improvement [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total charge- offs	(561)
Total recoveries	239
Bank Holding Company Accounting [Member] | Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total recoveries	4
Bank Holding Company Accounting [Member] | Medallion [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total charge- offs	(6,280)
Total recoveries	$ 194

[1] Beginning balance reflects the transition to Bank Holding Company Accounting by netting previously established unrealized depreciation against the gross loan balances resulting in a starting point of zero for this table.