Investment Securities (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investment Securities
Investment securities	$ 736,658	$ 810,238
Credit Loss Allowance	5,675
Purchases	22,408	98,258	$ 492,400
Acquisition of Infrastructure Lending Portfolio			65,060
Sales	7,940	7,326	16,427
Principal collections	83,533	205,660	382,924
VIE eliminations
Investment Securities
Purchases	(331,784)	(351,220)	(385,463)
Sales	(165,494)	(184,540)	(102,474)
Principal collections	(69,447)	(45,642)	(95,030)
Redemptions		(10,474)
Before consolidation of securitization VIEs
Investment Securities
Investment securities	2,162,228	2,215,275
Fair value option \| VIE eliminations
Investment Securities
Investment securities	(1,425,570)	(1,405,037)
Held-to-maturity
Investment Securities
Credit Loss Allowance	5,675	0
Purchases	22,408	91,162	463,810
Acquisition of Infrastructure Lending Portfolio			65,060
Principal collections	52,704	167,383	327,207
Held-to-maturity \| Before consolidation of securitization VIEs
Investment Securities
Investment securities	538,605	570,638
RMBS \| Available-for-sale
Investment Securities
Sales			13,264
Principal collections	26,000	26,929	34,763
Purchase Amortized Cost	123,292	138,580
Recorded Amortized Cost	123,292	138,580
Gross Unrealized Gains	44,123	51,310
Gross Unrealized Losses	(66)	(314)
Net Fair Value Adjustment	44,057	50,996
Fair Value	167,349	189,576
Portion of securities with variable rate	$ 144,900
Portion of securities with variable rate (as a percent)	86.60%
Cost of third party management	$ 800	1,500	1,800
Proceeds from sale of securities	$ 0	0	13,300
Realized gain on sale of securities			3,500
RMBS \| Available-for-sale \| One-month LIBOR
Investment Securities
Effective variable rate basis (as a percent)	0.144%
RMBS \| Available-for-sale \| B+
Investment Securities
Weighted Average Coupon (as a percent)	1.30%
WAL (Years)	5 years 8 months 12 days
RMBS \| Available-for-sale \| Before consolidation of securitization VIEs
Investment Securities
Investment securities	$ 167,349	189,576
RMBS \| Fair value option
Investment Securities
Purchases	282,368	120,103	90,982
Sales	135,567	41,501
Principal collections	44,197	16,500	1,439
Redemptions	10,500	10,474
Portion of securities with variable rate	0
RMBS \| Fair value option \| Before consolidation of securitization VIEs
Investment Securities
Investment securities	235,997	147,034
CMBS
Investment Securities
Amount not rated	179,500	186,600
CMBS \| Fair value option
Investment Securities
Purchases	49,416	238,213	323,071
Sales	37,867	150,365	105,637
Principal collections	30,079	40,490	$ 114,545
Portion of securities with variable rate	96,900
CMBS \| Fair value option \| Before consolidation of securitization VIEs
Investment Securities
Investment securities	1,209,030	1,295,363
Equity security \| Fair value option \| Before consolidation of securitization VIEs
Investment Securities
Investment securities	11,247	$ 12,664
Infrastructure bonds
Investment Securities
Credit Loss Allowance	$ 2,926

Amount of infrastructure lending portfolio acquired during the period.

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Represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor as trading before the adjustments for other-than-temporary impairments are recognized in earnings.

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Represents the cost to execute trading of available-for-sale securities by a third party manager engaged by the entity.

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Represents the percentage of the reference rate for the variable rate on available-for-sale securities as of the balance sheet date.

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Represents the investment securities that are not rated.

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Represents the amount of investment securities bearing variable interest rates.

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Represents the percentage of investment securities bearing variable interest rates.

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Represents the weighted average coupon interest rate on investment securities.

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Represents the weighted average life of investment securities.

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Cash inflow from proceeds from principal collections on investment securities.

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Total debt and equity financial instruments purchased during the period.

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The amount of redemption securities.

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Total debt and equity financial instruments sold during the period.

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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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Amount, before tax, of unrealized gain (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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Amount of realized gain (loss) 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 of allowance for credit loss for debt security measured at amortized cost (held-to-maturity).

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Amount of investment in marketable security.

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Fair value of securitized, pay-through debt securities collateralized by real estate mortgage loans classified as available-for-sale.

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Amount of cash inflow from sale 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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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