| Resale and Repurchase Agreements [Table Text Block] |
| | | | | | | | | | | | | | | | | | | | | | | | | Gross Amounts Not Offset in the Balance Sheet | | | (In thousands) | Gross Amount Recognized | Gross Amounts Offset in the Balance Sheet | Net Amounts Presented in the Balance Sheet | Financial Instruments Available for Offset | Securities Collateral Received/Pledged | Net Amount | | June 30, 2021 | | | | | | | Total resale agreements, subject to master netting arrangements | $ | 1,500,000 | | $ | (200,000) | | $ | 1,300,000 | | $ | — | | $ | (1,300,000) | | $ | — | | Total repurchase agreements, subject to master netting arrangements | 2,505,893 | | (200,000) | | 2,305,893 | | — | | (2,305,893) | | — | | | December 31, 2020 | | | | | | | Total resale agreements, subject to master netting arrangements | $ | 1,050,000 | | $ | (200,000) | | $ | 850,000 | | $ | — | | $ | (850,000) | | $ | — | | Total repurchase agreements, subject to master netting arrangements | 2,256,113 | | (200,000) | | 2,056,113 | | — | | (2,056,113) | | — | |
|
| Schedule of Underlying Assets of Repurchase Agreements [Table Text Block] |
| | | | | | | | | | | | | | | | Remaining Contractual Maturity of the Agreements | | | (In thousands) | Overnight and continuous | Up to 90 days | Greater than 90 days | Total | | June 30, 2021 | | | | | | Repurchase agreements, secured by: | | | | | | U.S. government and federal agency obligations | $ | 215,729 | | $ | 31,799 | | $ | 8,059 | | $ | 255,587 | | | | | | | | | | | | | Agency mortgage-backed securities | 1,712,923 | | 54,972 | | 222,475 | | 1,990,370 | | | Non-agency mortgage-backed securities | 42,656 | | — | | — | | 42,656 | | | Asset-backed securities | 183,979 | | — | | — | | 183,979 | | | Other debt securities | 33,301 | | — | | — | | 33,301 | | | Total repurchase agreements, gross amount recognized | $ | 2,188,588 | | $ | 86,771 | | $ | 230,534 | | $ | 2,505,893 | | | December 31, 2020 | | | | | | Repurchase agreements, secured by: | | | | | | U.S. government and federal agency obligations | $ | 150,305 | | $ | — | | $ | — | | $ | 150,305 | | | | | | | | | | | | | Agency mortgage-backed securities | 1,598,614 | | 34,018 | | 220,849 | | 1,853,481 | | | Non-agency mortgage-backed securities | 62,742 | | — | | — | | 62,742 | | | Asset-backed securities | 155,917 | | — | | — | | 155,917 | | | Other debt securities | 33,668 | | — | | — | | 33,668 | | | Total repurchase agreements, gross amount recognized | $ | 2,001,246 | | $ | 34,018 | | $ | 220,849 | | $ | 2,256,113 | |
|