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Debt Securities Available-for-Sale - Comparative Summary Of Mortgage-Backed Securities And Other Securities Available-for-Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 1,205,516	$ 1,246,673
Gross unrealized gains	7,824	18,862
Gross unrealized losses	(5,103)	(730)
Estimated fair value	1,208,237	1,264,805
U.S. Government agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	2,344	3,168
Gross unrealized gains	0	0
Gross unrealized losses	(54)	(10)
Estimated fair value	2,290	3,158
Pass-through certificates | GSE
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	579,035	270,867
Gross unrealized gains	5,233	10,720
Gross unrealized losses	(2,862)	(244)
Estimated fair value	581,406	281,343
Real estate mortgage investment conduits (REMICs)
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	969,790	1,155,285
Gross unrealized gains	7,631	17,747
Gross unrealized losses	(4,305)	(720)
Estimated fair value	973,116	1,172,312
Real estate mortgage investment conduits (REMICs) | GSE
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	390,755	884,414
Gross unrealized gains	2,398	7,027
Gross unrealized losses	(1,443)	(476)
Estimated fair value	391,710	890,965
Real estate mortgage investment conduits (REMICs) | Non-GSE
Schedule of Available-for-sale Securities [Line Items]
Amortized cost		4
Gross unrealized gains		0
Gross unrealized losses		0
Estimated fair value		4
Other debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	233,382	88,220
Gross unrealized gains	193	1,115
Gross unrealized losses	(744)	0
Estimated fair value	232,831	89,335
Other debt securities | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	71	122
Gross unrealized gains	1	1
Gross unrealized losses	0	0
Estimated fair value	72	123
Other debt securities | Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	233,311	87,319
Gross unrealized gains	192	1,099
Gross unrealized losses	(744)	0
Estimated fair value	$ 232,759	88,418
Other debt securities | Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized cost		779
Gross unrealized gains		15
Gross unrealized losses		0
Estimated fair value		$ 794

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- Definition

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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