Debt Securities Available-for-Sale - Gross Unrealized Losses on Mortgage-Backed Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Unrealized losses, less than 12 months	$ 2,065	$ 975
Estimated fair value, less than 12 months	193,449	201,038
Unrealized losses, 12 months or more	326	2,017
Estimated fair value, 12 months or more	25,034	125,378
Unrealized losses, total	2,391	2,992
Estimated fair value, total	218,483	326,416
GSE \| Pass-through Certificates
Debt Securities, Available-for-sale [Line Items]
Unrealized losses, less than 12 months	4	25
Estimated fair value, less than 12 months	109	3,404
Unrealized losses, 12 months or more	77	729
Estimated fair value, 12 months or more	634	55,184
Unrealized losses, total	81	754
Estimated fair value, total	743	58,588
GSE \| Real estate mortgage investment conduits (REMICs)
Debt Securities, Available-for-sale [Line Items]
Unrealized losses, less than 12 months	665	950
Estimated fair value, less than 12 months	135,392	197,634
Unrealized losses, 12 months or more	247	1,275
Estimated fair value, 12 months or more	24,351	54,555
Unrealized losses, total	912	2,225
Estimated fair value, total	159,743	252,189
Non-GSE \| Real estate mortgage investment conduits (REMICs)
Debt Securities, Available-for-sale [Line Items]
Unrealized losses, less than 12 months	0	0
Estimated fair value, less than 12 months	0	0
Unrealized losses, 12 months or more	2	0
Estimated fair value, 12 months or more	49	53
Unrealized losses, total	2	0
Estimated fair value, total	49	53
Corporate bonds \| Other debt obligations
Debt Securities, Available-for-sale [Line Items]
Unrealized losses, less than 12 months	1,396	0
Estimated fair value, less than 12 months	57,948	0
Unrealized losses, 12 months or more	0	13
Estimated fair value, 12 months or more	0	15,586
Unrealized losses, total	1,396	13
Estimated fair value, total	$ 57,948	$ 15,586

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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