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	Mar. 31, 2023	Dec. 31, 2022
Carrying Reported Amount Fair Value Disclosure [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Long-term debt	$ 2,467	$ 2,428
Medium-term notes	462	458
Investment agreements	233	233
Variable interest entity loans payable	2	2
Total liabilities	3,164	3,121
Gross liability (recoverable)	541	568
Ceded recoverable (liability)	8	15
Fair Value [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Long-term debt	296	330
Medium-term notes	309	310
Investment agreements	259	257
Variable interest entity loans payable	2	2
Total liabilities	866	899
Gross liability (recoverable)	876	864
Ceded recoverable (liability)	22	21
Fair Value [Member] | Fair Value Inputs Level 1 [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
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]
Long-term debt	296	330
Medium-term notes	0	0
Investment agreements	0	0
Variable interest entity loans payable	0	0
Total liabilities	296	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]
Long-term debt	0	0
Medium-term notes	309	310
Investment agreements	259	257
Variable interest entity loans payable	2	2
Total liabilities	570	569
Gross liability (recoverable)	876	864
Ceded recoverable (liability)	$ 22	$ 21