Income Taxes - Summary of Components of Deferred and Other Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Goodwill and other intangibles		$ (45,302)	$ (45,595)
Provision for loan losses		28,636	19,198
Net operating loss carryforwards	[1]	26,469	22,607
Accrued expenses, compensation, and other assets		997	1,701
Unrealized gains on other investments		(8,690)	(6,790)
Total deferred tax asset		2,110
Total deferred tax (liability)			(8,879)
Valuation allowance		(462)	(462)
Deferred tax asset (liability), net		1,648
Deferred Tax Liabilities			(9,341)
Taxes receivable		1,639	1,516
Net deferred and other tax assets (liabilities)		$ 3,287	$ (7,825)

[1] As of September 30, 2020, the Company and its subsidiaries had an estimated $101,627 of net operating loss carryforwards, $1,712 of which expire at various dates between December 31, 2026 and December 31, 2035, which had a net carrying value of $26,007 as of September 30, 2020.