Pledged Assets (Assets Pledged from Counterparties) (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024
Offsetting Assets and Liabilities [Line Items]
Obligation to Return Securities Borrowed Under Reverse Repurchase Agreements at Fair Value	$ 17,180,000	$ 16,676,000
Restricted Cash and Cash Equivalent	1,263,000	1,266,000	$ 1,368,000
Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted Cash and Cash Equivalent	20,000	66,000
Restricted Cash and Securities Pledged	17,517,000	16,968,000
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] \| Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	0	0
Restricted Cash and Cash Equivalent	2,000	38,000
Securities Sold under Agreements to Repurchase [Member] \| Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	(23,000)	(55,000)
Derivative [Member] \| Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted Cash and Securities Pledged	18,000	28,000
US Treasury Securities [Member] \| Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	(17,476,000)	(16,885,000)
Reverse Repurchase Agreements [Member] \| Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	(17,476,000)	(16,885,000)
Agency Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	(63,275,000)	(59,952,000)
Agency Securities [Member] \| Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	(21,000)
Reverse Repurchase Agreements [Member] \| US Treasury Securities [Member] \| Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	(17,476,000)	(16,885,000)
Derivative [Member] \| US Treasury Securities [Member] \| Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	0	0
Repurchase Agreements [Member] \| Agency Securities [Member] \| Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	(21,000)
Derivative [Member] \| Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted Cash and Cash Equivalent	18,000	28,000
Reverse Repurchase Agreements [Member] \| Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted Cash and Cash Equivalent	$ 0	$ 0