Investments (Unrealized Losses) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Investment securities available for sale:
Fair Value, Less than 12 months	$ 732,783	$ 2,778,014
Unrealized Losses, Less than 12 months	9,131	16,025
Fair Value, 12 months or more	217,427	332,953
Unrealized Losses, Greater than 12 months	1,056	1,794
Fair Value, Total	950,210	3,110,967
Unrealized Losses, Total	10,187	17,819
Investment securities held to maturity
Unrealized Losses, Total	0
Agency Securities
Investment securities available for sale:
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	447,983	347,081
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3,709	1,827
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	58,806	63,947
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	547	414
Fair Value, Total	506,789	411,028
Unrealized Losses, Total	4,256	2,241
Residential Mortgage Backed Securities
Investment securities available for sale:
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	172,628	2,387,293
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	302	14,016
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	149,170	264,257
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	392	1,371
Fair Value, Total	321,798	2,651,550
Unrealized Losses, Total	694	15,387
Investment securities held to maturity
Unrealized Losses, Total	0
Commercial Mortgage Backed Securities
Investment securities available for sale:
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		35,926
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		59
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer		0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0
Fair Value, Total		35,926
Unrealized Losses, Total	0	59
Investment securities held to maturity
Unrealized Losses, Total	0
Residential mortgage-backed securities
Investment securities held to maturity
Unrealized Losses, Total		0
Corporate bonds
Investment securities available for sale:
Fair Value, Total		12,463
Unrealized Losses, Total		132
Corporate Bonds
Investment securities available for sale:
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	112,172	7,714
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	5,120	123
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	9,451	4,749
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	117	9
Fair Value, Total	121,623
Unrealized Losses, Total	5,237
Other
Investment securities held to maturity
Unrealized Losses, Total	$ 0	$ 0

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