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Securities Available for sale, Unrealized Loss Position, Fair Value (Details) $ in Thousands | 12 Months Ended
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Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($)
Available for sale, Unrealized Loss Position [Line Items] |  |
Available for sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | 203 | 490
Available for sale, Securities in Unrealized Loss Position, Less than 12 Months [Abstract] |  |
Available for sale securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value | $ 2,182,644 | $ 700,064
Available for sale securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value | 897,351 | 5,631,803
Available for sale securities, Unrealized Loss Position, Fair Value | 3,079,995 | 6,331,867
Available for sale securities, Securities in Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available for sale securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 10,928 | 1,615
Available for sale securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 9,358 | 136,642
Available for sale securities, Unrealized Loss Position, Accumulated Loss | 20,286 | 138,257
Other than Temporary Impairment Loss, Available for sale, Recognized in Earnings | 0 | 0
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held | $ 36,000 | $ 45,000
U.S. Treasury [Member] |  |
Available for sale, Unrealized Loss Position [Line Items] |  |
Available for sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions |  | 1
Available for sale, Securities in Unrealized Loss Position, Less than 12 Months [Abstract] |  |
Available for sale securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value |  | $ 0
Available for sale securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value |  | 493
Available for sale securities, Unrealized Loss Position, Fair Value |  | 493
Available for sale securities, Securities in Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available for sale securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss |  | 0
Available for sale securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss |  | 3
Available for sale securities, Unrealized Loss Position, Accumulated Loss |  | $ 3
Residential agency mortgage-backed securities [Member] |  |
Available for sale, Unrealized Loss Position [Line Items] |  |
Available for sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | 133 | 289
Available for sale, Securities in Unrealized Loss Position, Less than 12 Months [Abstract] |  |
Available for sale securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value | $ 1,352,597 | $ 510,824
Available for sale securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value | 686,002 | 3,641,370
Available for sale securities, Unrealized Loss Position, Fair Value | 2,038,599 | 4,152,194
Available for sale securities, Securities in Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available for sale securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 6,690 | 1,158
Available for sale securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 8,423 | 96,606
Available for sale securities, Unrealized Loss Position, Accumulated Loss | $ 15,113 | $ 97,764
Commercial agency mortgage-backed securities [Member] |  |
Available for sale, Unrealized Loss Position [Line Items] |  |
Available for sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | 69 | 197
Available for sale, Securities in Unrealized Loss Position, Less than 12 Months [Abstract] |  |
Available for sale securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value | $ 830,047 | $ 179,258
Available for sale securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value | 210,877 | 1,969,504
Available for sale securities, Unrealized Loss Position, Fair Value | 1,040,924 | 2,148,762
Available for sale securities, Securities in Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available for sale securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 4,238 | 394
Available for sale securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 907 | 39,969
Available for sale securities, Unrealized Loss Position, Accumulated Loss | $ 5,145 | $ 40,363
Other debt securities [Member] |  |
Available for sale, Unrealized Loss Position [Line Items] |  |
Available for sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | 1 | 3
Available for sale, Securities in Unrealized Loss Position, Less than 12 Months [Abstract] |  |
Available for sale securities, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value | $ 0 | $ 9,982
Available for sale securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value | 472 | 20,436
Available for sale securities, Unrealized Loss Position, Fair Value | 472 | 30,418
Available for sale securities, Securities in Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available for sale securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 0 | 63
Available for sale securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 28 | 64
Available for sale securities, Unrealized Loss Position, Accumulated Loss | $ 28 | $ 127

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- Definition Available-for-sale Securities, Securities in Unrealized Loss Position, Accumulated Loss [Abstract] + References No definition available. + Details
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- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922890-210455 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=118942371&loc=SL82922954-210456 + Details
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- Definition Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922890-210455 + Details
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- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922890-210455 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=118942371&loc=SL82922954-210456 + Details
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- Definition Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922890-210455 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563 + Details
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