Derivative Instruments and Hedging Activities - Derivative Instruments in Statement of Financial Position, Fair Value (Details) - USD ($)	Jun. 30, 2026	Dec. 31, 2025
TBAs
Notional
Notional	$ (3,828,003,000)	$ (4,206,715,000)
Futures, net
Fair Value
Fair Value	0	0
Notional
Notional	(5,637,700,000)	(4,357,800,000)
Interest rate lock commitments
Fair Value
Fair Value	700,000	900,000
Notional
Notional	(39,600,000)	(49,600,000)
Balance Sheet Location [Axis]: us-gaap:DerivativeAssets
Fair Value
Fair Value	69,366,000	87,549,000
Notional
Notional	(4,316,594,000)	(2,601,018,000)
Balance Sheet Location [Axis]: us-gaap:DerivativeAssets \| Inverse interest-only securities
Fair Value
Fair Value	55,085,000	68,303,000
Notional
Notional	(1,061,841,000)	(1,233,247,000)
Balance Sheet Location [Axis]: us-gaap:DerivativeAssets \| Interest rate swap agreements
Fair Value
Fair Value	0	0
Notional
Notional	0	0
Balance Sheet Location [Axis]: us-gaap:DerivativeAssets \| TBAs
Fair Value
Fair Value	13,631,000	18,365,000
Notional
Notional	(3,215,696,000)	(5,676,000,000)
Balance Sheet Location [Axis]: us-gaap:DerivativeAssets \| Futures, net
Fair Value
Fair Value	0	0
Notional
Notional	0	(4,357,800,000)
Balance Sheet Location [Axis]: us-gaap:DerivativeAssets \| Interest rate lock commitments
Fair Value
Fair Value	650,000	881,000
Notional
Notional	(39,057,000)	(49,571,000)
Balance Sheet Location [Axis]: us-gaap:DerivativeLiabilities
Fair Value
Fair Value	(1,891,000)	(4,254,000)
Notional
Notional	(6,651,884,000)	(11,110,701,000)
Balance Sheet Location [Axis]: us-gaap:DerivativeLiabilities \| Inverse interest-only securities
Fair Value
Fair Value	0	0
Notional
Notional	0	0
Balance Sheet Location [Axis]: us-gaap:DerivativeLiabilities \| Interest rate swap agreements
Fair Value
Fair Value	0	0
Notional
Notional	(11,676,749,000)	(12,579,986,000)
Balance Sheet Location [Axis]: us-gaap:DerivativeLiabilities \| TBAs
Fair Value
Fair Value	(1,891,000)	(4,254,000)
Notional
Notional	(612,307,000)	(1,469,285,000)
Balance Sheet Location [Axis]: us-gaap:DerivativeLiabilities \| Futures, net
Fair Value
Fair Value	0	0
Notional
Notional	(5,637,700,000)	0
Balance Sheet Location [Axis]: us-gaap:DerivativeLiabilities \| Interest rate lock commitments
Fair Value
Fair Value	0	0
Notional
Notional	$ (528,000)	$ 0