Debt Securities Available for Sale - AFS debt securities in a continuous unrealized loss position (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	$ 409,520	$ 7,907,905
Less than 12 months Gross Unrealized Losses	10,331	437,310
12 months or more Fair Value	12,835,038	7,929,428
12 months or more Gross Unrealized Losses	1,853,813	1,322,381
Total Fair Value	13,244,558	15,837,333
Total Gross Unrealized Losses	1,864,144	1,759,691
US Treasury Securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	350,471	6,027,786
Less than 12 months Gross Unrealized Losses	8,546	288,582
12 months or more Fair Value	7,111,545	3,244,572
12 months or more Gross Unrealized Losses	375,928	209,696
Total Fair Value	7,462,016	9,272,358
Total Gross Unrealized Losses	384,474	498,278
Collateralized Mortgage Obligations - Federal agencies
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	8,212	139,845
Less than 12 months Gross Unrealized Losses	214	10,655
12 months or more Fair Value	127,961	22,661
12 months or more Gross Unrealized Losses	16,028	3,705
Total Fair Value	136,173	162,506
Total Gross Unrealized Losses	16,242	14,360
Mortgage Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	50,837	1,740,214
Less than 12 months Gross Unrealized Losses	1,571	138,071
12 months or more Fair Value	5,595,532	4,662,195
12 months or more Gross Unrealized Losses	1,461,857	1,108,980
Total Fair Value	5,646,369	6,402,409
Total Gross Unrealized Losses	$ 1,463,428	1,247,051
Other
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value		60
Less than 12 months Gross Unrealized Losses		2
12 months or more Fair Value		0
12 months or more Gross Unrealized Losses		0
Total Fair Value		60
Total Gross Unrealized Losses		$ 2