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Investment Securities, AFS and HTM Securities Gross Unrealized Losses (Details) $ in Thousands | Jun. 30, 2018 USD ($) security | Dec. 31, 2017 USD ($) security
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Unrealized losses and fair value of available for sale securities , by investment category and time length |  |
Unrealized losses on available for sale securities, less than 12 months | $ (41,975) | $ (15,099)
Unrealized losses on available for sale securities, 12 months or more | (81,093) | (52,868)
Total unrealized losses on available for sale securities | (123,068) | (67,967)
Fair value of unrealized losses on available for sale securities, less than 12 months | 1,939,830 | 1,593,503
Fair value of unrealized losses on available for sale securities, 12 months or more | 1,950,298 | 1,906,992
Total fair value of unrealized losses on available for sale securities | $ 3,890,128 | $ 3,500,495
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security | 110 | 92
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security | 120 | 105
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract] |  |
Unrealized losses on held to maturity securities, less than 12 months | $ (20,207) | $ (4,491)
Unrealized losses on held to maturity securities, 12 months or more | (36,648) | (21,331)
Total unrealized losses on held to maturity securities | $ (56,856) | $ (25,822)
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, 12 Months or Longer | security | 196 | 183
Fair value of unrealized losses on held to maturity securities, less than 12 months | $ 950,678 | $ 457,289
Fair value of unrealized losses on held to maturity securities, 12 months or more | 758,635 | 751,088
Total fair value of unrealized losses on held to maturity securities | $ 1,709,313 | $ 1,208,377
Held-to-maturity, Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions, less than 12 Months | security | 977 | 202
US Treasury Securities |  |
Unrealized losses and fair value of available for sale securities , by investment category and time length |  |
Unrealized losses on available for sale securities, less than 12 months | $ 0 |
Unrealized losses on available for sale securities, 12 months or more | (6) |
Total unrealized losses on available for sale securities | (6) |
Fair value of unrealized losses on available for sale securities, less than 12 months | 0 |
Fair value of unrealized losses on available for sale securities, 12 months or more | 996 |
Total fair value of unrealized losses on available for sale securities | $ 996 |
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security | 0 |
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security | 1 |
Obligations of state and political subdivisions (municipal securities) |  |
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract] |  |
Unrealized losses on held to maturity securities, less than 12 months | $ (10,814) | $ (746)
Unrealized losses on held to maturity securities, 12 months or more | (6,884) | (2,431)
Total unrealized losses on held to maturity securities | (17,698) | (3,177)
Fair value of unrealized losses on held to maturity securities, less than 12 months | 609,381 | 122,761
Fair value of unrealized losses on held to maturity securities, 12 months or more | 128,244 | 127,043
Total fair value of unrealized losses on held to maturity securities | $ 737,625 | $ 249,804
Obligations of state and political subdivisions (municipal securities) | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Less Than One Year [Member] |  |
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract] |  |
Number of held to maturity securities in a continuous unrealized loss position | security | 890 | 157
Obligations of state and political subdivisions (municipal securities) | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Greater Than Or Equal To One Year [Member] |  |
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract] |  |
Number of held to maturity securities in a continuous unrealized loss position | security | 142 | 132
Private Label |  |
Unrealized losses and fair value of available for sale securities , by investment category and time length |  |
Unrealized losses on available for sale securities, less than 12 months | $ 0 | $ 0
Unrealized losses on available for sale securities, 12 months or more | (5) | (8)
Total unrealized losses on available for sale securities | (5) | (8)
Fair value of unrealized losses on available for sale securities, less than 12 months | 0 | 0
Fair value of unrealized losses on available for sale securities, 12 months or more | 1,031 | 1,059
Total fair value of unrealized losses on available for sale securities | $ 1,031 | $ 1,059
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security | 0 | 0
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security | 1 | 1
GNMA Commercial Mortgage-Related Securities |  |
Unrealized losses and fair value of available for sale securities , by investment category and time length |  |
Unrealized losses on available for sale securities, less than 12 months | $ (8,821) | $ (5,554)
Unrealized losses on available for sale securities, 12 months or more | (43,577) | (28,347)
Total unrealized losses on available for sale securities | (52,398) | (33,901)
Fair value of unrealized losses on available for sale securities, less than 12 months | 284,733 | 480,514
Fair value of unrealized losses on available for sale securities, 12 months or more | 1,063,701 | 1,026,642
Total fair value of unrealized losses on available for sale securities | $ 1,348,434 | $ 1,507,156
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security | 22 | 33
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security | 80 | 70
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract] |  |
Unrealized losses on held to maturity securities, less than 12 months | $ (813) |
Unrealized losses on held to maturity securities, 12 months or more | (23,019) |
Total unrealized losses on held to maturity securities | (23,832) |
Fair value of unrealized losses on held to maturity securities, less than 12 months | 29,243 |
Fair value of unrealized losses on held to maturity securities, 12 months or more | 478,570 |
Total fair value of unrealized losses on held to maturity securities | $ 507,813 |
GNMA Commercial Mortgage-Related Securities | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Less Than One Year [Member] |  |
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract] |  |
Number of held to maturity securities in a continuous unrealized loss position | security | 1 |
GNMA Commercial Mortgage-Related Securities | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Greater Than Or Equal To One Year [Member] |  |
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract] |  |
Number of held to maturity securities in a continuous unrealized loss position | security | 24 |
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member] |  |
Unrealized losses and fair value of available for sale securities , by investment category and time length |  |
Unrealized losses on available for sale securities, less than 12 months | $ (111) | $ (13)
Unrealized losses on available for sale securities, 12 months or more | 0 | 0
Total unrealized losses on available for sale securities | (111) | (13)
Fair value of unrealized losses on available for sale securities, less than 12 months | 100,757 | 12,158
Fair value of unrealized losses on available for sale securities, 12 months or more | 0 | 0
Total fair value of unrealized losses on available for sale securities | $ 100,757 | $ 12,158
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security | 7 | 1
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security | 0 | 0
Other Debt And Other Equity Securities |  |
Unrealized losses and fair value of available for sale securities , by investment category and time length |  |
Unrealized losses on available for sale securities, less than 12 months |  | $ (12)
Unrealized losses on available for sale securities, 12 months or more |  | 0
Total unrealized losses on available for sale securities |  | (12)
Fair value of unrealized losses on available for sale securities, less than 12 months |  | 188
Fair value of unrealized losses on available for sale securities, 12 months or more |  | 0
Total fair value of unrealized losses on available for sale securities |  | $ 188
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security |  | 1
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security |  | 0
Equity Securities [Member] |  |
Unrealized losses and fair value of available for sale securities , by investment category and time length |  |
Unrealized losses on available for sale securities, less than 12 months |  | $ (14)
Unrealized losses on available for sale securities, 12 months or more |  | 0
Total unrealized losses on available for sale securities |  | (14)
Fair value of unrealized losses on available for sale securities, less than 12 months |  | 1,487
Fair value of unrealized losses on available for sale securities, 12 months or more |  | 0
Total fair value of unrealized losses on available for sale securities |  | $ 1,487
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security |  | 3
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security |  | 0
FNMA and FHLMC | US Treasury Securities |  |
Unrealized losses and fair value of available for sale securities , by investment category and time length |  |
Unrealized losses on available for sale securities, less than 12 months |  | $ (7)
Unrealized losses on available for sale securities, 12 months or more |  | 0
Total unrealized losses on available for sale securities |  | (7)
Fair value of unrealized losses on available for sale securities, less than 12 months |  | 996
Fair value of unrealized losses on available for sale securities, 12 months or more |  | 0
Total fair value of unrealized losses on available for sale securities |  | $ 996
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security |  | 1
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security |  | 0
FNMA and FHLMC | Residential Related Securities |  |
Unrealized losses and fair value of available for sale securities , by investment category and time length |  |
Unrealized losses on available for sale securities, less than 12 months | $ (1,613) | $ (572)
Unrealized losses on available for sale securities, 12 months or more | (3,620) | (2,062)
Total unrealized losses on available for sale securities | (5,233) | (2,634)
Fair value of unrealized losses on available for sale securities, less than 12 months | 100,946 | 69,939
Fair value of unrealized losses on available for sale securities, 12 months or more | 128,509 | 142,093
Total fair value of unrealized losses on available for sale securities | $ 229,455 | $ 212,032
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security | 19 | 9
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security | 9 | 9
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract] |  |
Unrealized losses on held to maturity securities, less than 12 months | $ (1,518) | $ (73)
Unrealized losses on held to maturity securities, 12 months or more | (788) | (417)
Total unrealized losses on held to maturity securities | (2,306) | (490)
Fair value of unrealized losses on held to maturity securities, less than 12 months | 76,046 | 13,143
Fair value of unrealized losses on held to maturity securities, 12 months or more | 14,728 | 16,262
Total fair value of unrealized losses on held to maturity securities | $ 90,774 | $ 29,405
FNMA and FHLMC | Residential Related Securities | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Less Than One Year [Member] |  |
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract] |  |
Number of held to maturity securities in a continuous unrealized loss position | security | 25 | 8
FNMA and FHLMC | Residential Related Securities | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Greater Than Or Equal To One Year [Member] |  |
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract] |  |
Number of held to maturity securities in a continuous unrealized loss position | security | 10 | 10
GNMA | Residential Related Securities |  |
Unrealized losses and fair value of available for sale securities , by investment category and time length |  |
Unrealized losses on available for sale securities, less than 12 months | $ (31,430) | $ (8,927)
Unrealized losses on available for sale securities, 12 months or more | (33,885) | (22,451)
Total unrealized losses on available for sale securities | (65,315) | (31,378)
Fair value of unrealized losses on available for sale securities, less than 12 months | 1,453,394 | 1,028,221
Fair value of unrealized losses on available for sale securities, 12 months or more | 756,061 | 737,198
Total fair value of unrealized losses on available for sale securities | $ 2,209,455 | $ 1,765,419
Number of available for sale securities in a continuous unrealized loss position less than twelve months | security | 62 | 44
Number of available for sale securities in a continuous unrealized loss position for twelve months or more | security | 29 | 25
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract] |  |
Unrealized losses on held to maturity securities, less than 12 months | $ (7,062) | $ (3,373)
Unrealized losses on held to maturity securities, 12 months or more | (5,957) | (3,026)
Total unrealized losses on held to maturity securities | (13,019) | (6,399)
Fair value of unrealized losses on held to maturity securities, less than 12 months | 236,008 | 268,388
Fair value of unrealized losses on held to maturity securities, 12 months or more | 137,093 | 120,892
Total fair value of unrealized losses on held to maturity securities | $ 373,101 | $ 389,280
GNMA | Residential Related Securities | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Less Than One Year [Member] |  |
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract] |  |
Number of held to maturity securities in a continuous unrealized loss position | security | 61 | 35
GNMA | Residential Related Securities | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Greater Than Or Equal To One Year [Member] |  |
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract] |  |
Number of held to maturity securities in a continuous unrealized loss position | security | 20 | 18
GNMA | GNMA Commercial Mortgage-Related Securities |  |
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract] |  |
Unrealized losses on held to maturity securities, less than 12 months |  | $ (299)
Unrealized losses on held to maturity securities, 12 months or more |  | (15,457)
Total unrealized losses on held to maturity securities |  | (15,756)
Fair value of unrealized losses on held to maturity securities, less than 12 months |  | 52,997
Fair value of unrealized losses on held to maturity securities, 12 months or more |  | 486,891
Total fair value of unrealized losses on held to maturity securities |  | $ 539,888
GNMA | GNMA Commercial Mortgage-Related Securities | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Less Than One Year [Member] |  |
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract] |  |
Number of held to maturity securities in a continuous unrealized loss position | security |  | 2
GNMA | GNMA Commercial Mortgage-Related Securities | Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Greater Than Or Equal To One Year [Member] |  |
Held-to-maturity Securities Continuous Unrealized Loss Position [Abstract] |  |
Number of held to maturity securities in a continuous unrealized loss position | security |  | 23

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