Investment Securities - Credit Quality Indicators (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Held-to-maturity debt securities, at amortized cost	$ 98,202	$ 16,592
Municipal bonds and notes
Financing Receivable, Credit Quality Indicator [Line Items]
Held-to-maturity debt securities, at amortized cost	7,157	3,635
Corporate bonds
Financing Receivable, Credit Quality Indicator [Line Items]
Held-to-maturity debt securities, at amortized cost	712	0
Aaa | Municipal bonds and notes
Financing Receivable, Credit Quality Indicator [Line Items]
Held-to-maturity debt securities, at amortized cost	3,774	2,070
Aaa | Corporate bonds
Financing Receivable, Credit Quality Indicator [Line Items]
Held-to-maturity debt securities, at amortized cost	39	0
Aa1 | Municipal bonds and notes
Financing Receivable, Credit Quality Indicator [Line Items]
Held-to-maturity debt securities, at amortized cost	2,031	1,145
Aa1 | Corporate bonds
Financing Receivable, Credit Quality Indicator [Line Items]
Held-to-maturity debt securities, at amortized cost	0	0
Aa2 | Municipal bonds and notes
Financing Receivable, Credit Quality Indicator [Line Items]
Held-to-maturity debt securities, at amortized cost	1,154	420
Aa2 | Corporate bonds
Financing Receivable, Credit Quality Indicator [Line Items]
Held-to-maturity debt securities, at amortized cost	42	0
Aa3 | Municipal bonds and notes
Financing Receivable, Credit Quality Indicator [Line Items]
Held-to-maturity debt securities, at amortized cost	172	0
Aa3 | Corporate bonds
Financing Receivable, Credit Quality Indicator [Line Items]
Held-to-maturity debt securities, at amortized cost	105	0
A1 | Municipal bonds and notes
Financing Receivable, Credit Quality Indicator [Line Items]
Held-to-maturity debt securities, at amortized cost	26	0
A1 | Corporate bonds
Financing Receivable, Credit Quality Indicator [Line Items]
Held-to-maturity debt securities, at amortized cost	251	0
A2 | Corporate bonds
Financing Receivable, Credit Quality Indicator [Line Items]
Held-to-maturity debt securities, at amortized cost	264	0
A3 | Corporate bonds
Financing Receivable, Credit Quality Indicator [Line Items]
Held-to-maturity debt securities, at amortized cost	$ 11	$ 0