Consolidating Financial Statements (details) - Consolidating Balance Sheet (Unaudited) - USD ($) shares in Millions, $ in Millions	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Consolidating Balance Sheet
Fixed maturities, available for sale, at fair value	$ 61,907	$ 60,515
Equity securities, available for sale, at fair value	700	732
Real estate investments	920	928
Short-term securities	5,292	4,865
Other investments	3,512	3,448
Total investments	72,331	70,488
Cash	328	307	$ 265	$ 380
Investment income accrued	602	630
Premiums receivable	7,345	6,722
Reinsurance recoverables	8,150	8,287
Ceded unearned premiums	665	589
Deferred acquisition costs	2,051	1,923
Deferred taxes	201	465
Contractholder receivables	4,700	4,609
Goodwill	3,589	3,580
Other intangible assets	264	268
Other assets	2,443	2,377
Total assets	102,669	100,245
Claims and claim adjustment expense reserves	48,574	47,949
Unearned premium reserves	13,052	12,329
Contractholder payables	4,700	4,609
Payables for reinsurance premiums	364	273
Debt	6,920	6,437
Other liabilities	5,201	5,427
Total liabilities	78,811	77,024
Common stock	22,781	22,614
Retained earnings	33,016	32,196
Accumulated other comprehensive income (loss)	(344)	(755)
Treasury stock, at cost	(31,595)	(30,834)
Total shareholders' equity	23,858	23,221	24,714
Total liabilities and shareholders' equity	102,669	100,245
Fixed maturities, available for sale, amortized cost	60,482	59,650
Equity securities, available for sale, cost	$ 558	$ 504
Common stock, shares authorized	1,750.0	1,750.0
Common stock, shares issued	275.9	279.6
Common stock, shares outstanding	275.9	279.6
Treasury stock, at cost, shares	495.7	489.5
Reportable Legal Entities [Member] | TPC [Member]
Consolidating Balance Sheet
Fixed maturities, available for sale, at fair value	$ 43,029	$ 42,014
Equity securities, available for sale, at fair value	176	169
Real estate investments	55	56
Short-term securities	2,065	2,447
Other investments	2,612	2,569
Total investments	47,937	47,255
Cash	134	141	121	225
Investment income accrued	422	441
Premiums receivable	4,952	4,545
Reinsurance recoverables	5,594	5,664
Ceded unearned premiums	587	536
Deferred acquisition costs	1,847	1,741
Deferred taxes	(43)	216
Contractholder receivables	3,759	3,656
Goodwill	2,586	2,578
Other intangible assets	202	202
Other assets	2,122	1,973
Total assets	70,099	68,948
Claims and claim adjustment expense reserves	32,564	32,168
Unearned premium reserves	9,043	8,575
Contractholder payables	3,759	3,656
Payables for reinsurance premiums	214	156
Debt	693	693
Other liabilities	3,956	4,106
Total liabilities	50,229	49,354
Additional paid-in capital	11,634	11,634
Retained earnings	7,917	7,933
Accumulated other comprehensive income (loss)	319	27
Total shareholders' equity	19,870	19,594
Total liabilities and shareholders' equity	70,099	68,948
Reportable Legal Entities [Member] | Other Subsidiaries [Member]
Consolidating Balance Sheet
Fixed maturities, available for sale, at fair value	18,829	18,452
Equity securities, available for sale, at fair value	357	408
Real estate investments	865	872
Short-term securities	715	791
Other investments	899	878
Total investments	21,665	21,401
Cash	192	164	141	153
Investment income accrued	176	183
Premiums receivable	2,393	2,177
Reinsurance recoverables	2,556	2,623
Ceded unearned premiums	78	53
Deferred acquisition costs	204	182
Deferred taxes	188	224
Contractholder receivables	941	953
Goodwill	1,003	1,002
Other intangible assets	62	66
Other assets	283	370
Total assets	29,741	29,398
Claims and claim adjustment expense reserves	16,010	15,781
Unearned premium reserves	4,009	3,754
Contractholder payables	941	953
Payables for reinsurance premiums	150	117
Other liabilities	1,040	1,239
Total liabilities	22,150	21,844
Common stock	390	390
Additional paid-in capital	6,499	6,499
Retained earnings	706	797
Accumulated other comprehensive income (loss)	(4)	(132)
Total shareholders' equity	7,591	7,554
Total liabilities and shareholders' equity	29,741	29,398
Reportable Legal Entities [Member] | TRV [Member]
Consolidating Balance Sheet
Fixed maturities, available for sale, at fair value	49	49
Equity securities, available for sale, at fair value	167	155
Short-term securities	2,512	1,627
Other investments	1	1
Total investments	2,729	1,832
Cash	2	2	$ 3	$ 2
Investment income accrued	4	6
Deferred taxes	56	25
Investment in subsidiaries	27,451	27,137
Other assets	38	34
Total assets	30,280	29,036
Debt	6,227	5,744
Other liabilities	205	82
Total liabilities	6,432	5,826
Common stock	22,781	22,614
Retained earnings	33,006	32,185
Accumulated other comprehensive income (loss)	(344)	(755)
Treasury stock, at cost	(31,595)	(30,834)
Total shareholders' equity	23,848	23,210
Total liabilities and shareholders' equity	30,280	29,036
Eliminations [Member]
Consolidating Balance Sheet
Investment in subsidiaries	(27,451)	(27,137)
Total assets	(27,451)	(27,137)
Common stock	(390)	(390)
Additional paid-in capital	(18,133)	(18,133)
Retained earnings	(8,613)	(8,719)
Accumulated other comprehensive income (loss)	(315)	105
Total shareholders' equity	(27,451)	(27,137)
Total liabilities and shareholders' equity	$ (27,451)	$ (27,137)