Debt Securities Available for Sale - Weighted average yield and contractual maturities of debt securities AFS (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Amortized cost
Amortized Cost	$ 19,462,981	$ 18,101,163
Allowance for credit losses
Allowance for credit losses	500	0
Gross unrealized gains
Gross unrealized gains	725	1,394
Gross unrealized loss
Gross unrealized losses	1,445,782	1,373,513
Fair Value
Debt securities available-for-sale	$ 18,017,424	$ 16,729,044
Weighted average yield
Weighted Average Yield	2.72%	2.35%
US Treasury Securities
Amortized cost
Amortized cost - Within 1 year	$ 9,394,716	$ 7,103,518
Amortized cost - After 1 to 5 years	2,825,336	3,598,209
Amortized cost - After 5 to 10 years	307,174	307,512
Amortized Cost	12,527,226	11,009,239
Allowance for credit losses
Allowance for credit losses - Within 1 year	0
Allowance for credit losses - After 1 to 5 years	0
Allowance for credit losses - After 5 to 10 years	0
Allowance for credit losses	0
Gross unrealized gains
Gross unrealized gain - Within 1 year	68	526
Gross unrealized gain - After 1 to 5 years	0	84
Gross unrealized gain - After 5 to 10 years	0	0
Gross unrealized gains	68	610
Gross unrealized loss
Gross unrealized losses - Within 1 year	60,864	59,415
Gross unrealized losses - After 1 to 5 years	140,775	170,209
Gross unrealized losses - After 5 to 10 years	36,444	33,164
Gross unrealized losses	238,083	262,788
Fair Value
Fair value - Within 1 year	9,333,920	7,044,629
Fair value - After 1 to 5 years	2,684,561	3,428,084
Fair value - After 5 to 10 years	270,730	274,348
Debt securities available-for-sale	$ 12,289,211	$ 10,747,061
Weighted average yield
Weighted average yield - Within 1 year	3.90%	3.51%
Weighted average yield - After 1 to 5 years	1.32%	1.35%
Weighted average yield - After 5 to 10 years	1.63%	1.63%
Weighted Average Yield	3.26%	2.75%
Collateralized Mortgage Obligations - Federal agencies
Amortized cost
Amortized cost - After 1 to 5 years	$ 15,883	$ 17,899
Amortized cost - After 5 to 10 years	19,189	20,503
Amortized cost - After 10 years	104,671	108,280
Amortized Cost	139,743	146,682
Allowance for credit losses
Allowance for credit losses - After 1 to 5 years	0
Allowance for credit losses - After 5 to 10 years	0
Allowance for credit losses - After 10 years	0
Allowance for credit losses	0
Gross unrealized gains
Gross unrealized gain - After 1 to 5 years	0	0
Gross unrealized gain - After 5 to 10 years	0	2
Gross unrealized gain - After 10 years	21	29
Gross unrealized gains	21	31
Gross unrealized loss
Gross unrealized losses - After 1 to 5 years	813	838
Gross unrealized losses - After 5 to 10 years	1,337	1,321
Gross unrealized losses - After 10 years	10,006	9,868
Gross unrealized losses	12,156	12,027
Fair Value
Fair value - After 1 to 5 years	15,070	17,061
Fair value - After 5 to 10 years	17,852	19,184
Fair value - After 10 years	94,686	98,441
Debt securities available-for-sale	$ 127,608	$ 134,686
Weighted average yield
Weighted average yield - After 1 to 5 years	1.54%	1.55%
Weighted average yield - After 5 to 10 years	2.29%	2.28%
Weighted average yield - After 10 years	2.55%	2.54%
Weighted Average Yield	2.40%	2.38%
Mortgage Backed Securities - federal agencies
Amortized cost
Amortized cost - Within 1 year	$ 457	$ 637
Amortized cost - After 1 to 5 years	78,628	82,310
Amortized cost - After 5 to 10 years	817,332	792,431
Amortized cost - After 10 years	5,897,090	6,067,353
Amortized Cost	6,793,507	6,942,731
Allowance for credit losses
Allowance for credit losses - Within 1 year	0
Allowance for credit losses - After 1 to 5 years	0
Allowance for credit losses - After 5 to 10 years	0
Allowance for credit losses - After 10 years	0
Allowance for credit losses	0
Gross unrealized gains
Gross unrealized gain - Within 1 year	0	0
Gross unrealized gain - After 1 to 5 years	6	11
Gross unrealized gain - After 5 to 10 years	181	75
Gross unrealized gain - After 10 years	449	667
Gross unrealized gains	636	753
Gross unrealized loss
Gross unrealized losses - Within 1 year	5	3
Gross unrealized losses - After 1 to 5 years	3,683	3,536
Gross unrealized losses - After 5 to 10 years	56,576	48,250
Gross unrealized losses - After 10 years	1,135,279	1,046,909
Gross unrealized losses	1,195,543	1,098,698
Fair Value
Fair value - Within 1 year	452	634
Fair value - After 1 to 5 years	74,951	78,785
Fair value - After 5 to 10 years	760,937	744,256
Fair value - After 10 years	4,762,260	5,021,111
Debt securities available-for-sale	$ 5,598,600	$ 5,844,786
Weighted average yield
Weighted average yield - Within 1 year	2.06%	3.72%
Weighted average yield - After 1 to 5 years	2.36%	2.34%
Weighted average yield - After 5 to 10 years	2.33%	2.28%
Weighted average yield - After 10 years	1.65%	1.64%
Weighted Average Yield	1.74%	1.72%
Other
Amortized cost
Amortized cost - Within 1 year	$ 1,005	$ 1,011
Amortized cost - After 1 to 5 years	1,500	1,500
Amortized Cost	2,505	2,511
Allowance for credit losses
Allowance for credit losses - Within 1 year	500
Allowance for credit losses - After 1 to 5 years	0
Allowance for credit losses	500
Gross unrealized gains
Gross unrealized gain - Within 1 year	0	0
Gross unrealized gain - After 1 to 5 years	0	0
Gross unrealized gains	0	0
Gross unrealized loss
Gross unrealized losses - Within 1 year	0	0
Gross unrealized losses - After 1 to 5 years	0	0
Gross unrealized losses	0	0
Fair Value
Fair value - Within 1 year	505	1,011
Fair value - After 1 to 5 years	1,500	1,500
Debt securities available-for-sale	$ 2,005	$ 2,511
Weighted average yield
Weighted average yield - Within 1 year	4.00%	4.00%
Weighted average yield - After 1 to 5 years	8.50%	8.50%
Weighted Average Yield	6.69%	6.69%