Fair Value Measurements - Fair Value of Assets And Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	$ 8,450	$ 9,362
Equity securities, estimated fair value	392	657
Servicing related assets	21	27
Total assets	8,863	10,046
Servicing related liabilities	12	9
U.S. Treasury bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	147	123
Municipal bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	1,462	1,649
Foreign government bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	200	227
Governmental agency bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	129	177
Governmental agency mortgage-backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	5,050	5,607
U.S. corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	1,003	1,081
Foreign corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	459	498
Preferred Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Equity securities, estimated fair value	14	17
Common Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Equity securities, estimated fair value	378	640
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	0	0
Equity securities, estimated fair value	392	657
Servicing related assets	0	0
Total assets	392	657
Servicing related liabilities	0	0
Level 1 | U.S. Treasury bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	0	0
Level 1 | Municipal bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	0	0
Level 1 | Foreign government bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	0	0
Level 1 | Governmental agency bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	0	0
Level 1 | Governmental agency mortgage-backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	0	0
Level 1 | U.S. corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	0	0
Level 1 | Foreign corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	0	0
Level 1 | Preferred Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Equity securities, estimated fair value	14	17
Level 1 | Common Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Equity securities, estimated fair value	378	640
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	8,450	9,362
Equity securities, estimated fair value	0	0
Servicing related assets	1	11
Total assets	8,451	9,373
Servicing related liabilities	0	0
Level 2 | U.S. Treasury bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	147	123
Level 2 | Municipal bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	1,462	1,649
Level 2 | Foreign government bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	200	227
Level 2 | Governmental agency bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	129	177
Level 2 | Governmental agency mortgage-backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	5,050	5,607
Level 2 | U.S. corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	1,003	1,081
Level 2 | Foreign corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	459	498
Level 2 | Preferred Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Equity securities, estimated fair value	0	0
Level 2 | Common Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Equity securities, estimated fair value	0	0
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	0	0
Equity securities, estimated fair value	0	0
Servicing related assets	20	16
Total assets	20	16
Servicing related liabilities	12	9
Level 3 | U.S. Treasury bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	0	0
Level 3 | Municipal bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	0	0
Level 3 | Foreign government bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	0	0
Level 3 | Governmental agency bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	0	0
Level 3 | Governmental agency mortgage-backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	0	0
Level 3 | U.S. corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	0	0
Level 3 | Foreign corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Debt securities, estimated fair value	0	0
Level 3 | Preferred Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Equity securities, estimated fair value	0	0
Level 3 | Common Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Equity securities, estimated fair value	$ 0	$ 0