Debt Securities Available for Sale - AFS debt securities in a continuous unrealized loss position (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	$ 680,831	$ 287,277
Less than 12 months Gross Unrealized Losses	2,940	5,566
12 months or more Fair Value	9,995,950	12,455,131
12 months or more Gross Unrealized Losses	1,047,242	1,367,947
Total Fair Value	10,676,781	12,742,408
Total Gross Unrealized Losses	1,050,182	1,373,513
US Treasury Securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	651,502	244,925
Less than 12 months Gross Unrealized Losses	2,369	5,126
12 months or more Fair Value	4,457,595	6,550,941
12 months or more Gross Unrealized Losses	108,458	257,662
Total Fair Value	5,109,097	6,795,866
Total Gross Unrealized Losses	110,827	262,788
Collateralized Mortgage Obligations - Federal agencies
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	1,909	5,234
Less than 12 months Gross Unrealized Losses	2	35
12 months or more Fair Value	109,743	124,930
12 months or more Gross Unrealized Losses	8,192	11,992
Total Fair Value	111,652	130,164
Total Gross Unrealized Losses	8,194	12,027
Mortgage Backed Securities - federal agencies
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	27,420	37,118
Less than 12 months Gross Unrealized Losses	569	405
12 months or more Fair Value	5,428,612	5,779,260
12 months or more Gross Unrealized Losses	930,592	1,098,293
Total Fair Value	5,456,032	5,816,378
Total Gross Unrealized Losses	$ 931,161	$ 1,098,698