Debt Securities Available-for-Sale - Gross Unrealized Losses on Mortgage-Backed Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Unrealized losses, less than 12 months	$ (14)	$ (21,199)
Estimated fair value, less than 12 months	1,065	430,053
Unrealized losses, 12 months or more	(66,936)	(46,238)
Estimated fair value, 12 months or more	742,624	504,194
Unrealized losses, total	(66,950)	(67,437)
Estimated fair value, total	743,689	934,247
U.S. Government agency securities
Debt Securities, Available-for-sale [Line Items]
Unrealized losses, less than 12 months	0	(3,942)
Estimated fair value, less than 12 months	0	71,058
Unrealized losses, 12 months or more	(3,589)	(132)
Estimated fair value, 12 months or more	72,309	1,018
Unrealized losses, total	(3,589)	(4,074)
Estimated fair value, total	72,309	72,076
Pass-through Certificates | GSE
Debt Securities, Available-for-sale [Line Items]
Unrealized losses, less than 12 months	(11)	(8,112)
Estimated fair value, less than 12 months	302	142,605
Unrealized losses, 12 months or more	(43,525)	(32,234)
Estimated fair value, 12 months or more	346,732	289,890
Unrealized losses, total	(43,536)	(40,346)
Estimated fair value, total	347,034	432,495
Real estate mortgage investment conduits (REMICs) | GSE
Debt Securities, Available-for-sale [Line Items]
Unrealized losses, less than 12 months	0	(8,303)
Estimated fair value, less than 12 months	0	180,612
Unrealized losses, 12 months or more	(15,347)	(7,843)
Estimated fair value, 12 months or more	221,560	84,112
Unrealized losses, total	(15,347)	(16,146)
Estimated fair value, total	221,560	264,724
Other debt securities | Municipal bonds
Debt Securities, Available-for-sale [Line Items]
Unrealized losses, less than 12 months	(3)
Estimated fair value, less than 12 months	763
Unrealized losses, 12 months or more	0
Estimated fair value, 12 months or more	0
Unrealized losses, total	(3)
Estimated fair value, total	763
Other debt securities | Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Unrealized losses, less than 12 months	0	(842)
Estimated fair value, less than 12 months	0	35,778
Unrealized losses, 12 months or more	(4,475)	(6,029)
Estimated fair value, 12 months or more	102,023	129,174
Unrealized losses, total	(4,475)	(6,871)
Estimated fair value, total	$ 102,023	$ 164,952