Income Taxes - Schedule of Reconciliation Between Provision for Income Taxes and Amount Computed by Applying Federal Statutory Income Tax Rate (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Federal income taxes at statutory rate	$ 1,679	$ 1,149	$ 844
Increase (decrease) in provision for income taxes as a result of:
State income taxes, net of federal tax benefit	164	105	107
Income tax credits, net of amortization	(195)	(178)	(86)
Tax-exempt interest	(86)	(99)	(69)
Other, net	(6)	4	(14)
Provision for income taxes	$ 1,556	$ 981	$ 782
Effective Income Tax Rate Reconciliation, Tax Credit, Percent [Abstract]
Federal Income Taxes at Stuatory Rate, Percent	21.00%	21.00%	21.00%
State income taxes, net of federal tax benefit	2.10%	1.90%	2.70%
Income tax credits, net of amortization	(2.40%)	(3.30%)	(2.10%)
Tax-exempt interest	(1.10%)	(1.80%)	(1.80%)
Other, net	(0.10%)	0.10%	(0.30%)
Effective Income Tax Rate, Percent	19.50%	17.90%	19.50%