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Investment Securities, Equity Securities with Readily Determinable Fair Values and Other Investments (Details) - USD ($) $ in Thousands | Jun. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Held-to-maturity securities |  |
Amortized cost | $ 3,400 | $ 3,400
Estimated fair value | 3,400 | 3,400
Carrying Value | 3,400 | 3,400
Available-for-sale securities |  |
Amortized cost | 4,148,673 | 3,054,289
Available for sale debt securities | 4,171,881 | 3,080,768
Total Amortized cost | 4,148,673 | 3,054,289
Total Gross unrealized gains | 29,901 | 35,832
Total Gross unrealized losses | 6,693 | 9,353
Estimate of Fair Value Measurement |  |
Available-for-sale securities |  |
Available for sale debt securities and equity securities | 4,171,881 | 3,080,768
Reported Value Measurement [Member] |  |
Available-for-sale securities |  |
Available for sale debt securities and equity securities | 4,171,881 | 3,080,768
Residential mortgage-backed securities |  |
Available-for-sale securities |  |
Amortized cost | 4,103,989 | 3,006,592
Gross unrealized gains | 26,331 | 32,701
Gross unrealized losses | (6,684) | (9,339)
Residential mortgage-backed securities | Estimate of Fair Value Measurement |  |
Available-for-sale securities |  |
Available for sale debt securities | 4,123,636 | 3,029,954
Residential mortgage-backed securities | Reported Value Measurement [Member] |  |
Available-for-sale securities |  |
Available for sale debt securities | 4,123,636 | 3,029,954
US Government Corporations and Agencies Securities [Member] |  |
Available-for-sale securities |  |
Available for sale debt securities | 917,895 | 371,407
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] |  |
Available-for-sale securities |  |
Available for sale debt securities | 3,205,741 | 2,658,547
States and political subdivisions |  |
Available-for-sale securities |  |
Amortized cost | 44,684 | 47,697
Gross unrealized gains | 3,570 | 3,131
Gross unrealized losses | (9) | (14)
States and political subdivisions | Estimate of Fair Value Measurement |  |
Available-for-sale securities |  |
Available for sale debt securities | 48,245 | 50,814
States and political subdivisions | Reported Value Measurement [Member] |  |
Available-for-sale securities |  |
Available for sale debt securities | 48,245 | 50,814
Other Debt Obligations [Member] |  |
Held-to-maturity securities |  |
Amortized cost | 3,400 | 3,400
Estimated fair value | 3,400 | 3,400
Carrying Value | $ 3,400 | $ 3,400

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