Securities Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value (Details) $ in Thousands	Mar. 31, 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	232	77
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 3,903,355	$ 1,143,562
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	445,591	438,846
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	4,348,946	1,582,408
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	67,232	8,197
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,161	642
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 68,393	$ 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	81	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 186,267	$ 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	186,267	6,166
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3,781	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	$ 3,781	$ 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	90	38
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 3,005,975	$ 786,890
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	139,714	160,747
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	3,145,689	947,637
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	44,828	6,605
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	427	120
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 45,255	$ 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	60	37
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 711,113	$ 350,506
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	305,406	277,627
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,016,519	628,133
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	18,623	1,587
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	705	494
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 19,328	$ 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	471	472
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	471	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	29	28
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 29	$ 28