Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Equity securities	$ 59,556		$ 57,336
Other assets	80,583		78,815
Accrued expenses and other liabilities	79,438		71,210
Long-term debt	187,764		207,588
Retained earnings	203,870		201,136
Supplemental cash flow information - Noncash activities
Transfers from available-for-sale debt securities to held-to-maturity debt securities	0	$ 3,687
Reclassification of long-term debt to accrued expenses and other liabilities	4,927	0
Fixed rate securities [Member]
Supplemental cash flow information - Noncash activities
Transfers from held-to-maturity debt securities to available-for-sale debt securities	$ 0	$ 23,919
Cumulative effect from change in accounting policies, period of adoption adjustment [Member] | Accounting Standards Update 2023-02 Cumulative Effect Period of Adoption [Member]
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Equity securities			1,700
Other assets			548
Accrued expenses and other liabilities			7,333
Long-term debt			(4,927)
Retained earnings			(158)
Cumulative effect from change in accounting policies, period of adoption adjusted balance [Member] | Accounting Standards Update 2023-02 Cumulative Effect Period of Adoption [Member]
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Equity securities			59,036
Other assets			79,363
Accrued expenses and other liabilities			78,543
Long-term debt			202,661
Retained earnings			$ 200,978