Fair Value of Financial Instruments (Fair Value Hierarchy Table Presents The Company's Assets And Liabilities At Fair Value Not Recorded On The Company's Consolidated Balance Sheet) (Detail) - Value Disclosed At Fair Value Not Recorded At Fair Value [Member] - Fair Value Measurements Nonrecurring [Member] - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Carrying Reported Amount Fair Value Disclosure [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Other investments	$ 3
Total assets	3
Long-term debt	2,546	$ 2,428
Medium-term notes	457	458
Investment agreements	225	233
Variable interest entity loans payable	3	2
Total liabilities	3,231	3,121
Gross liability (recoverable)	513	568
Ceded recoverable (liability)	17	15
Fair Value [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Other investments	3
Total assets	3
Long-term debt	272	330
Medium-term notes	286	310
Investment agreements	238	257
Variable interest entity loans payable	3	2
Total liabilities	799	899
Gross liability (recoverable)	764	864
Ceded recoverable (liability)	19	21
Fair Value [Member] | Fair Value Inputs Level 1 [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Other investments	0
Total assets	0
Long-term debt	0	0
Medium-term notes	0	0
Investment agreements	0	0
Variable interest entity loans payable	0	0
Total liabilities	0	0
Gross liability (recoverable)	0	0
Ceded recoverable (liability)	0	0
Fair Value [Member] | Fair Value Inputs Level 2 [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Other investments	0
Total assets	0
Long-term debt	272	330
Medium-term notes	0	0
Investment agreements	0	0
Variable interest entity loans payable	0	0
Total liabilities	272	330
Gross liability (recoverable)	0	0
Ceded recoverable (liability)	0	0
Fair Value [Member] | Fair Value Inputs Level 3 [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Other investments	3
Total assets	3
Long-term debt	0	0
Medium-term notes	286	310
Investment agreements	238	257
Variable interest entity loans payable	3	2
Total liabilities	527	569
Gross liability (recoverable)	764	864
Ceded recoverable (liability)	$ 19	$ 21