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Securities Available for sale, Unrealized Loss Position, Fair Value (Details) $ in Thousands	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Available for sale, Unrealized Loss Position [Line Items]
Available for sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	77	203
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	$ 1,143,562	$ 2,182,644
Available for sale securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	438,846	897,351
Available for sale securities, Unrealized Loss Position, Fair Value	1,582,408	3,079,995
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	8,197	10,928
Available for sale securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	642	9,358
Available for sale securities, Unrealized Loss Position, Accumulated Loss	8,839	$ 20,286
Debt Securities, Available-for-sale, Allowance for Credit Loss	$ 0
Municipal securities [Member]
Available for sale, Unrealized Loss Position [Line Items]
Available for sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	1	0
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	$ 6,166	$ 0
Available for sale securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	0	0
Available for sale securities, Unrealized Loss Position, Fair Value	6,166	0
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	5	0
Available for sale securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Available for sale securities, Unrealized Loss Position, Accumulated Loss	$ 5	$ 0
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	38	133
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	$ 786,890	$ 1,352,597
Available for sale securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	160,747	686,002
Available for sale securities, Unrealized Loss Position, Fair Value	947,637	2,038,599
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	6,605	6,690
Available for sale securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	120	8,423
Available for sale securities, Unrealized Loss Position, Accumulated Loss	$ 6,725	$ 15,113
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	37	69
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	$ 350,506	$ 830,047
Available for sale securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	277,627	210,877
Available for sale securities, Unrealized Loss Position, Fair Value	628,133	1,040,924
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	1,587	4,238
Available for sale securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	494	907
Available for sale securities, Unrealized Loss Position, Accumulated Loss	$ 2,081	$ 5,145
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	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	$ 0
Available for sale securities, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	472	472
Available for sale securities, Unrealized Loss Position, Fair Value	472	472
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	0
Available for sale securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	28	28
Available for sale securities, Unrealized Loss Position, Accumulated Loss	$ 28	$ 28

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Available-for-sale Securities, Securities in Unrealized Loss Position, Accumulated Loss [Abstract]

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Amount of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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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.

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