Derivative Financial Instruments - Offsetting of Derivative Assets - Derivative Liabilities, Financial Liabilities, and Collateral Held by Counterparty (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	$ 7,155,594	$ 8,733,656
Financial instruments	(7,138,415)	(8,692,756)
Net amount of liabilities in the consolidated balance sheet	17,179	40,900
Bank of America, N.A.
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	1,208,837	1,294,213
Financial instruments	(1,204,238)	(1,294,213)
Net amount of liabilities in the consolidated balance sheet	4,599
Atlas Securitized Products, L.P.
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	1,870,521	1,938,756
Financial instruments	(1,870,521)	(1,938,756)
Wells Fargo Bank, N.A.
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	670,412	795,119
Financial instruments	(670,412)	(789,305)
Net amount of liabilities in the consolidated balance sheet		5,814
Royal Bank of Canada
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	728,528	785,597
Financial instruments	(728,528)	(785,597)
JPMorgan Chase Bank, N.A.
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	662,918	1,220,822
Financial instruments	(662,918)	(1,214,559)
Net amount of liabilities in the consolidated balance sheet		6,263
BNP Paribas
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	414,500	568,790
Financial instruments	(414,500)	(568,790)
Citibank, N.A.
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	512,559	455,426
Financial instruments	(512,559)	(455,426)
Barclays Capital
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	36,090	258,559
Financial instruments	(36,090)	(254,750)
Net amount of liabilities in the consolidated balance sheet		3,809
Santander US Capital Markets LLC
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	230,345	282,077
Financial instruments	(230,345)	(282,077)
Goldman Sachs
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	161,997	336,894
Financial instruments	(157,927)	(336,624)
Net amount of liabilities in the consolidated balance sheet	4,070	270
Morgan Stanley Bank, N.A.
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	414,996	472,659
Financial instruments	(414,996)	(472,659)
Nomura Corporate Funding Americas
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	118,478	175,000
Financial instruments	(118,478)	(175,000)
Mizuho Bank, Ltd.
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	116,903	125,000
Financial instruments	(116,903)	(125,000)
Others
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	3,176	1,363
Net amount of liabilities in the consolidated balance sheet	3,176	1,363
PennyMac Mortgage Investment Trust
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	7,097
Net amount of liabilities in the consolidated balance sheet	7,097
Interest rate lock commitments
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	5,334	23,381
Net amount of liabilities in the consolidated balance sheet	$ 5,334	$ 23,381