Schedule II-Condensed Financial Information Of Registrant (Balance Sheets) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 4,937	$ 3,934	$ 3,609	$ 4,075
Fixed maturity securities (Parent Company - amortized cost of $592 and $589)	19,676	16,692
Equity securities, current	1,009	1,493
Other invested assets, current	13	21
Other receivables	2,634	2,558
Income taxes receivable	335	10
Securities lending collateral	353	604
Other current assets	2,319	2,104
Total current assets	39,033	34,321
Fixed maturity securities (Parent Company - amortized cost $0)	505	487
Equity securities	30	33
Other invested assets, long-term	4,228	3,726
Property and equipment, net	3,133	2,735
Other noncurrent assets	1,350	758
Total assets	77,453	71,571
Current liabilities:
Accounts payable and accrued expenses	4,198	4,959
Security trades pending payable	84	197
Securities lending payable	351	604
Current portion of long-term debt	1,598	849
Other current liabilities	3,692	3,190
Total current liabilities	23,617	21,965
Long-term debt, less current portion	17,787	17,217
Other noncurrent liabilities	1,420	1,182
Total liabilities	45,725	43,030
Commitments and contingencies-Note 5
Shareholders' equity
Preferred stock, without par value, shares authorized - 100,000,000; shares issued and outstanding - none	0	0
Common stock, par value $0.01, shares authorized - 900,000,000; shares issued and outstanding - 252,922,161 and 257,395,577	3	3
Additional paid-in capital	9,448	9,536
Retained earnings	22,573	19,988
Accumulated other comprehensive loss	(296)	(986)
Total shareholders' equity	31,728	28,541	26,503	25,101
Total liabilities and shareholders' equity	77,453	71,571
Parent Company [Member]
Current assets:
Cash and cash equivalents	1,818	1,290	$ 956	$ 883
Fixed maturity securities (Parent Company - amortized cost of $592 and $589)	602	573
Equity securities, current	253	86
Other invested assets, current	4	10
Other receivables	92	131
Income taxes receivable	170	0
Net due from subsidiaries	602	170
Securities lending collateral	17	35
Other current assets	462	320
Total current assets	4,020	2,615
Equity securities	6	6
Other invested assets, long-term	651	616
Property and equipment, net	170	186
Deferred tax assets, net	216	209
Investment in subsidiaries	47,423	44,877
Other noncurrent assets	263	225
Total assets	52,749	48,734
Current liabilities:
Accounts payable and accrued expenses	887	1,429
Security trades pending payable	9	0
Securities lending payable	17	35
Income taxes payable	0	112
Current portion of long-term debt	1,598	849
Other current liabilities	237	235
Total current liabilities	2,748	2,660
Long-term debt, less current portion	17,762	17,192
Other noncurrent liabilities	511	341
Total liabilities	21,021	20,193
Commitments and contingencies-Note 5
Shareholders' equity
Preferred stock, without par value, shares authorized - 100,000,000; shares issued and outstanding - none	0	0
Common stock, par value $0.01, shares authorized - 900,000,000; shares issued and outstanding - 252,922,161 and 257,395,577	3	3
Additional paid-in capital	9,448	9,536
Retained earnings	22,573	19,988
Accumulated other comprehensive loss	(296)	(986)
Total shareholders' equity	31,728	28,541
Total liabilities and shareholders' equity	$ 52,749	$ 48,734