Securities Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value (Details) $ in Thousands	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	388	77
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 4,863,909	$ 1,143,562
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	836,045	438,846
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	5,699,954	1,582,408
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	60,096	8,197
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	11,280	642
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 71,376	$ 8,839
Municipal securities [Member]
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	140	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 362,508	$ 6,166
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	362,508	6,166
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	4,145	5
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 4,145	$ 5
Residential agency mortgage-backed securities [Member]
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	100	38
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 2,384,362	$ 786,890
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	429,246	160,747
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,813,608	947,637
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	29,149	6,605
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	8,705	120
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 37,854	$ 6,725
Commercial agency mortgage-backed securities [Member]
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	147	37
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 2,117,039	$ 350,506
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	406,327	277,627
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,523,366	628,133
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	26,802	1,587
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	2,547	494
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 29,349	$ 2,081
Other debt securities [Member]
Debt Securities, 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, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	472	472
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	472	472
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, Continuous Unrealized Loss Position, Accumulated Loss	$ 28	$ 28