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Securities (Tables) | 6 Months Ended
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Jun. 30, 2020
Marketable Securities [Abstract] |
Trading Securities, [Table Text Block] | The fair value and net unrealized gain (loss) included in trading securities are as follows (in thousands):
|  | June 30, 2020 |  |  |  | December 31, 2019 |  |
|  | Fair Value |  | Net Unrealized Gain (Loss) |  | Fair Value |  | Net Unrealized Gain (Loss)
U.S. government agency debentures |  | $ | 4,237 |  |  | $ | 19 |  |  | $ | 44,264 |  |  | $ | 6 |
Residential agency mortgage-backed securities |  | 1,146,454 |  |  | 3,589 |  |  | 1,504,651 |  |  | 2,293 |
Municipal and other tax-exempt securities |  | 22,710 |  |  | 116 |  |  | 26,196 |  |  | 60 |
Asset-backed securities |  | 5 |  |  | — |  |  | 14,084 |  |  | (21) |
Other debt securities |  | 22,699 |  |  | 127 |  |  | 34,726 |  |  | 21 |
Total trading securities |  | $ | 1,196,105 |  |  | $ | 3,851 |  |  | $ | 1,623,921 |  |  | $ | 2,359 |
Investment Securities (Held-to-Maturity) [Table Text Block] | The amortized cost and fair values of investment securities are as follows (in thousands):
|  | June 30, 2020 |  |  |  |  |  |
|  | Amortized |  | Fair |  | Gross Unrealized |  |
|  | Cost |  | Value |  | Gain |  | Loss
Municipal and other tax-exempt |  | $ | 84,239 |  |  | $ | 88,623 |  |  | $ | 4,384 |  |  | $ | — |
Residential agency mortgage-backed securities |  | 9,812 |  |  | 10,734 |  |  | 922 |  |  | — |
Other debt securities |  | 175,565 |  |  | 199,769 |  |  | 24,235 |  |  | (31) |
Total investment securities |  | 269,616 |  |  | 299,126 |  |  | 29,541 |  |  | (31) |
Allowance for credit losses1 |  | (1,628) |  |  |  |  |  |  |
Investment securities, net of allowance |  | 267,988 |  |  | 299,126 |  |  | 29,541 |  |  | (31) |
1 Effective with the adoption of FASB ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326) on January 1, 2020.
|  | December 31, 2019 |  |  |  |  |  |
|  | Amortized |  | Fair |  | Gross Unrealized |  |
|  | Cost |  | Value |  | Gain |  | Loss
Municipal and other tax-exempt |  | $ | 93,653 |  |  | $ | 96,897 |  |  | $ | 3,250 |  |  | $ | (6) |
Residential agency mortgage-backed securities |  | 10,676 |  |  | 11,164 |  |  | 488 |  |  | — |
Other debt securities |  | 189,089 |  |  | 206,341 |  |  | 17,547 |  |  | (295) |
Total investment securities |  | $ | 293,418 |  |  | $ | 314,402 |  |  | $ | 21,285 |  |  | $ | (301) |
The amortized cost and fair values of investment securities at June 30, 2020, by contractual maturity, are as shown in the following table (dollars in thousands):
|  | Less than One Year |  | One to Five Years |  | Six to Ten Years |  | Over Ten Years |  | Total |  | Weighted Average Maturity1
Fixed maturity debt securities: |  |  |  |  |  |  |  |  |  |  |  |
Amortized cost |  | $ | 39,734 |  |  | $ | 87,863 |  |  | $ | 122,309 |  |  | $ | 9,898 |  |  | $ | 259,804 |  |  | 4.95 |
Fair value |  | 40,151 |  |  | 96,615 |  |  | 141,378 |  |  | 10,248 |  |  | 288,392 |  |  |
Residential mortgage-backed securities: |  |  |  |  |  |  |  |  |  |  |  |
Amortized cost |  |  |  |  |  |  |  |  |  | $ | 9,812 |  |  | 2
Fair value |  |  |  |  |  |  |  |  |  | 10,734 |  |  |
Total investment securities: |  |  |  |  |  |  |  |  |  |  |  |
Amortized cost |  |  |  |  |  |  |  |  |  | $ | 269,616 |  |  |
Fair value |  |  |  |  |  |  |  |  |  | 299,126 |  |  |
1Expected maturities may differ from contractual maturities, because borrowers may have the right to call or prepay obligations with or without penalty. 2The average expected lives of residential mortgage-backed securities were 4.6 years based upon current prepayment assumptions. Temporarily Impaired Investment Securities (in thousands):
|  | June 30, 2020 |  |  |  |  |  |  |  |  |  |  |  |
|  | Number of Securities |  | Less Than 12 Months |  |  |  | 12 Months or Longer |  |  |  | Total |  |
|  |  |  | Fair Value |  | Unrealized Loss |  | Fair Value |  | Unrealized Loss |  | Fair Value |  | Unrealized Loss
Investment: |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other debt securities |  | 4 |  |  | — |  |  | — |  |  | 2,142 |  |  | 31 |  |  | 2,142 |  |  | 31 |
Total investment securities |  | 4 |  |  | $ | — |  |  | $ | — |  |  | $ | 2,142 |  |  | $ | 31 |  |  | $ | 2,142 |  |  | $ | 31 |
|  | December 31, 2019 |  |  |  |  |  |  |  |  |  |  |  |
|  | Number of Securities |  | Less Than 12 Months |  |  |  | 12 Months or Longer |  |  |  | Total |  |
|  |  |  | Fair Value |  | Unrealized Loss |  | Fair Value |  | Unrealized Loss |  | Fair Value |  | Unrealized Loss
Investment: |  |  |  |  |  |  |  |  |  |  |  |  |  |
Municipal and other tax-exempt |  | 4 |  |  | $ | 1,001 |  |  | $ | 1 |  |  | $ | 1,706 |  |  | $ | 5 |  |  | $ | 2,707 |  |  | $ | 6 |
Other debt securities |  | 13 |  |  | 275 |  |  | 1 |  |  | 8,041 |  |  | 294 |  |  | 8,316 |  |  | 295 |
Total investment securities |  | 17 |  |  | $ | 1,276 |  |  | $ | 2 |  |  | $ | 9,747 |  |  | $ | 299 |  |  | $ | 11,023 |  |  | $ | 301 |
Available For Sale Securities [Table Text Block] | The amortized cost and fair value of available for sale securities are as follows (in thousands):
|  | June 30, 2020 |  |  |  |  |  |  |  |
|  | Amortized |  | Fair |  | Gross Unrealized |  |  |  |
|  | Cost |  | Value |  | Gain |  | Loss |  |
U.S. Treasury |  | $ | 900 |  |  | $ | 912 |  |  | $ | 12 |  |  | $ | — |  |  |
Municipal and other tax-exempt |  | 29,670 |  |  | 31,240 |  |  | 1,570 |  |  | — |  |  |
Mortgage-backed securities: |  |  |  |  |  |  |  |  |  |
Residential agency |  | 8,789,466 |  |  | 9,147,238 |  |  | 360,056 |  |  | (2,284) |  |  |
Residential non-agency |  | 21,941 |  |  | 35,250 |  |  | 13,318 |  |  | (9) |  |  |
Commercial agency |  | 3,146,108 |  |  | 3,260,807 |  |  | 116,042 |  |  | (1,343) |  |  |
Other debt securities |  | 500 |  |  | 472 |  |  | — |  |  | (28) |  |  |
Total available for sale securities |  | $ | 11,988,585 |  |  | $ | 12,475,919 |  |  | $ | 490,998 |  |  | $ | (3,664) |  |  |
|  | December 31, 2019 |  |  |  |  |  |  |  |
|  | Amortized |  | Fair |  | Gross Unrealized |  |  |  |
|  | Cost |  | Value |  | Gain |  | Loss |  |
U.S. Treasury |  | $ | 1,598 |  |  | $ | 1,600 |  |  | $ | 2 |  |  | $ | — |  |  |
Municipal and other tax-exempt |  | 1,789 |  |  | 1,861 |  |  | 72 |  |  | — |  |  |
Mortgage-backed securities: |  |  |  |  |  |  |  |  |  |
Residential agency |  | 7,956,297 |  |  | 8,046,096 |  |  | 104,912 |  |  | (15,113) |  |  |
Residential non-agency |  | 25,968 |  |  | 41,609 |  |  | 15,641 |  |  | — |  |  |
Commercial agency |  | 3,145,342 |  |  | 3,178,005 |  |  | 37,808 |  |  | (5,145) |  |  |
Other debt securities |  | 500 |  |  | 472 |  |  | — |  |  | (28) |  |  |
Total available for sale securities |  | $ | 11,131,494 |  |  | $ | 11,269,643 |  |  | $ | 158,435 |  |  | $ | (20,286) |  |  |
The amortized cost and fair values of available for sale securities at June 30, 2020, by contractual maturity, are as shown in the following table (dollars in thousands):
| Less than One Year |  | One to Five Years |  | Six to Ten Years |  | Over Ten Years |  | Total |  | Weighted Average Maturity1
Fixed maturity debt securities: |  |  |  |  |  |  |  |  |  |  |
Amortized cost | $ | 34,044 |  |  | $ | 1,321,471 |  |  | $ | 1,241,310 |  |  | $ | 580,353 |  |  | $ | 3,177,178 |  |  | 8.03 |
Fair value | 34,144 |  |  | 1,375,128 |  |  | 1,280,251 |  |  | 603,908 |  |  | 3,293,431 |  |  |
Residential mortgage-backed securities: |  |  |  |  |  |  |  |  |  |  |
Amortized cost |  |  |  |  |  |  |  |  | $ | 8,811,407 |  |  | 2
Fair value |  |  |  |  |  |  |  |  | 9,182,488 |  |  |
Total available-for-sale securities: |  |  |  |  |  |  |  |  |  |  |
Amortized cost |  |  |  |  |  |  |  |  | $ | 11,988,585 |  |  |
Fair value |  |  |  |  |  |  |  |  | 12,475,919 |  |  |
1Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without penalty. 2The average expected lives of residential mortgage-backed securities were 3.1 years based upon current prepayment assumptions. Sales of available for sale securities resulted in gains and losses as follows (in thousands):
| Three Months Ended June 30, |  |  |  | Six Months Ended June 30, |  |
| 2020 |  | 2019 |  | 2020 |  | 2019
Proceeds | $ | 179,051 |  |  | $ | 122,098 |  |  | $ | 205,945 |  |  | $ | 367,357 |
Gross realized gains | 5,580 |  |  | 1,029 |  |  | 5,583 |  |  | 6,327 |
Gross realized losses | — |  |  | — |  |  | — |  |  | (5,222) |
Related federal and state income tax expense (benefit) | 1,421 |  |  | 262 |  |  | 1,422 |  |  | 281 |
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value [Table Text Block] |
|  | June 30, 2020 |  |  |  |  |  |  |  |  |  |  |  |
|  | Number of Securities |  | Less Than 12 Months |  |  |  | 12 Months or Longer |  |  |  | Total |  |
|  |  |  | Fair Value |  | Unrealized Loss |  | Fair Value |  | Unrealized Loss |  | Fair Value |  | Unrealized Loss
Available for sale: |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage-backed securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |
Residential agency |  | 36 |  |  | 492,864 |  |  | 1,375 |  |  | 173,997 |  |  | 909 |  |  | 666,861 |  |  | 2,284 |
Residential non-agency |  | 1 |  |  | 1,695 |  |  | 9 |  |  | — |  |  | — |  |  | 1,695 |  |  | 9 |
Commercial agency |  | 22 |  |  | 271,735 |  |  | 902 |  |  | 160,806 |  |  | 441 |  |  | 432,541 |  |  | 1,343 |
Other debt securities |  | 1 |  |  | — |  |  | — |  |  | 472 |  |  | 28 |  |  | 472 |  |  | 28 |
Total available for sale securities |  | 60 |  |  | $ | 766,294 |  |  | $ | 2,286 |  |  | $ | 335,275 |  |  | $ | 1,378 |  |  | $ | 1,101,569 |  |  | $ | 3,664 |
|  | December 31, 2019 |  |  |  |  |  |  |  |  |  |  |  |
|  | Number of Securities |  | Less Than 12 Months |  |  |  | 12 Months or Longer |  |  |  | Total |  |
|  |  |  | Fair Value |  | Unrealized Loss |  | Fair Value |  | Unrealized Loss |  | Fair Value |  | Unrealized Loss
Available for sale: |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage-backed securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |
Residential agency |  | 133 |  |  | $ | 1,352,597 |  |  | $ | 6,690 |  |  | $ | 686,002 |  |  | $ | 8,423 |  |  | $ | 2,038,599 |  |  | $ | 15,113 |
Commercial agency |  | 69 |  |  | 830,047 |  |  | 4,238 |  |  | 210,877 |  |  | 907 |  |  | 1,040,924 |  |  | 5,145 |
Other debt securities |  | 1 |  |  | — |  |  | — |  |  | 472 |  |  | 28 |  |  | 472 |  |  | 28 |
Total available for sale securities |  | 203 |  |  | $ | 2,182,644 |  |  | $ | 10,928 |  |  | $ | 897,351 |  |  | $ | 9,358 |  |  | $ | 3,079,995 |  |  | $ | 20,286 |
Fair Value Option Securities [Table Text Block] | The fair value and net unrealized gain (loss) included in fair value option securities is as follows (in thousands):
|  | June 30, 2020 |  |  |  | December 31, 2019 |  |
|  | Fair Value |  | Net Unrealized Gain (Loss) |  | Fair Value |  | Net Unrealized Gain (Loss)
U.S. Treasury |  | $ | 92,742 |  |  | $ | 307 |  |  | $ | 9,917 |  |  | $ | (48) |
Residential agency mortgage-backed securities |  | 629,915 |  |  | 16,549 |  |  | 1,088,660 |  |  | 14,109 |
Total |  | $ | 722,657 |  |  | $ | 16,856 |  |  | $ | 1,098,577 |  |  | $ | 14,061 |

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