Debt Securities Available-for-Sale - Comparative Summary of Mortgage-Backed Securities and Other Securities Available-for-Sale) (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Estimated fair value	$ 810,649	$ 1,019,607
Gross unrealized gains	0	3
Gross unrealized losses	(66,950)	(67,437)
Estimated fair value	743,699	952,173
U.S. Government agency securities
Debt Securities, Available-for-sale [Line Items]
Estimated fair value	75,898	76,150
Gross unrealized gains	0	0
Gross unrealized losses	(3,589)	(4,074)
Estimated fair value	72,309	72,076
Pass-through certificates, GSE
Debt Securities, Available-for-sale [Line Items]
Estimated fair value	390,580	472,963
Gross unrealized gains	0	1
Gross unrealized losses	(43,536)	(40,346)
Estimated fair value	347,044	432,618
GSE
Debt Securities, Available-for-sale [Line Items]
Estimated fair value	236,907	280,870
Gross unrealized gains	0	0
Gross unrealized losses	(15,347)	(16,146)
Estimated fair value	221,560	264,724
Real estate mortgage investment conduits (REMICs)
Debt Securities, Available-for-sale [Line Items]
Estimated fair value	627,487	753,833
Gross unrealized gains	0	1
Gross unrealized losses	(58,883)	(56,492)
Estimated fair value	568,604	697,342
Municipal bonds
Debt Securities, Available-for-sale [Line Items]
Estimated fair value	766	21
Gross unrealized gains	0	0
Gross unrealized losses	(3)	0
Estimated fair value	763	21
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Estimated fair value	106,498	189,603
Gross unrealized gains	0	2
Gross unrealized losses	(4,475)	(6,871)
Estimated fair value	102,023	182,734
Other debt securities
Debt Securities, Available-for-sale [Line Items]
Estimated fair value	107,264	189,624
Gross unrealized gains	0	2
Gross unrealized losses	(4,478)	(6,871)
Estimated fair value	$ 102,786	$ 182,755