Investment Securities - AFS and Fair Value Option (Details) $ in Thousands	Mar. 31, 2021 USD ($) security	Dec. 31, 2020 USD ($) security
Unrealized Losses
Number of securities with unrealized losses \| security	1	2
RMBS
Estimated Fair Value
Securities with a loss less than 12 months		$ 438
Securities with a loss greater than 12 months	$ 1,170	1,195
Unrealized Losses
Securities with a loss less than 12 months		(25)
Securities with a loss greater than 12 months	(34)	$ (41)
Portion of securities with variable rate	139,400
RMBS \| Fair value option
Unrealized Losses
Fair value of investment securities before consolidation of VIEs	249,000
Unpaid principal balance of investment securities before consolidation of VIEs	160,100
Portion of securities with variable rate	0
CMBS \| Fair value option
Unrealized Losses
Fair value of investment securities before consolidation of VIEs	1,200,000
Unpaid principal balance of investment securities before consolidation of VIEs	2,700,000
Portion of securities with variable rate	96,900
VIE eliminations
Unrealized Losses
Fair value of investment securities before consolidation of VIEs eliminated against VIE liabilities	$ 19,300

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Represents the fair value balance of the investment securities before consolidation of the VIEs.

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Represents the fair value balance of the investment securities before consolidation of the VIEs that is eliminated against VIE liabilities.

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Represents the unpaid principal balance of the investment securities before consolidation of the VIEs.

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Represents the amount of investment securities bearing variable interest rates.

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Number of securities with unrealized losses.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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