Investment Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	$ 198,141	$ 202,929
Gross Unrealized Gains	12,734	14,077
Gross Unrealized Losses	(6,698)	(2,749)
Estimated Fair Value	204,177	214,257
Interest receivable	61,700	63,400
Available-for-sale Securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Interest receivable	1,700	1,600
Residential mortgage-backed securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	4,556	4,991
Gross Unrealized Gains	132	275
Gross Unrealized Losses	0	0
Estimated Fair Value	4,688	5,266
Tax-exempt asset-backed securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	178,872	183,225
Gross Unrealized Gains	12,602	13,802
Gross Unrealized Losses	0	0
Estimated Fair Value	191,474	197,027
Credit risk transfer securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	14,713	14,713
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(6,698)	(2,749)
Estimated Fair Value	$ 8,015	$ 11,964

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

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