Securities - Summary of AFS Securities Portfolio (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	$ 856,283	$ 1,008,921
Gross Unrealized gains	13,154	12,872
Gross Unrealized losses	(5,659)	(6,827)
Allowance for credit losses ("ACL")	(2,371)
Estimated Fair Value	861,407	1,014,966
Other
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	1,399	1,386
Gross Unrealized gains	94	63
Estimated Fair Value	1,493	1,449
Agency Mortgage-backed Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	761,247	905,949
Gross Unrealized gains	11,884	9,174
Gross Unrealized losses		(146)
Estimated Fair Value	773,131	914,977
Beneficial interest - FHLMC securitizations
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	36,637	47,586
Gross Unrealized gains	241	1,801
Gross Unrealized losses	(5,551)	(6,681)
Allowance for credit losses ("ACL")	(2,371)
Estimated Fair Value	28,956	42,706
Corporate Bonds
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	57,000	54,000
Gross Unrealized gains	935	1,834
Gross Unrealized losses	(108)
Estimated Fair Value	$ 57,827	$ 55,834

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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