Consolidating Financial Statements (details) - Consolidating Statement of Income (Unaudited) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Consolidating Statement of Income
Premiums		$ 6,209	$ 6,032	$ 18,257	$ 17,851
Net investment income		582	614	1,675	1,838
Fee income		116	116	352	345
Net realized investment gains (losses)	[1]	23	15	33	35
Other revenues		31	21	115	68
Total revenues		6,961	6,798	20,432	20,137
Claims and claim adjustment expenses		3,856	3,382	11,330	10,360
Amortization of deferred acquisition costs		1,012	987	2,972	2,913
General and administrative expenses		1,057	1,028	3,106	3,055
Interest expense		89	94	273	278
Total claims and expenses		6,014	5,491	17,681	16,606
Income before income taxes		947	1,307	2,751	3,531
Income tax expense (benefit)		231	379	680	958
Net income		716	928	2,071	2,573
Total other-than-temporary impairment losses		(4)	(14)	(36)	(26)
Other-than-temporary impairment losses recognized in net realized investment gains (losses)		(4)	(14)	(26)	(23)
Other-than-temporary impairment gains (losses) recognized in other comprehensive income		0	0	(10)	(3)
TPC [Member]
Consolidating Statement of Income
Premiums		4,246	4,110	12,492	12,150
Net investment income		389	400	1,142	1,235
Fee income		116	116	352	345
Net realized investment gains (losses)		10	5	(7)	24
Other revenues		24	15	105	55
Total revenues		4,785	4,646	14,084	13,809
Claims and claim adjustment expenses		2,615	2,264	7,710	6,982
Amortization of deferred acquisition costs		683	663	1,999	1,956
General and administrative expenses		744	715	2,191	2,134
Interest expense		11	12	35	36
Total claims and expenses		4,053	3,654	11,935	11,108
Income before income taxes		732	992	2,149	2,701
Income tax expense (benefit)		194	293	584	742
Net income		538	699	1,565	1,959
Total other-than-temporary impairment losses		(1)	(5)	(18)	(13)
Other-than-temporary impairment losses recognized in net realized investment gains (losses)		(1)	(5)	(13)	(11)
Other-than-temporary impairment gains (losses) recognized in other comprehensive income				(5)	(2)
Other Subsidiaries [Member]
Consolidating Statement of Income
Premiums		1,963	1,922	5,765	5,701
Net investment income		190	213	524	599
Net realized investment gains (losses)		12	10	39	10
Other revenues		11	6	28	13
Total revenues		2,176	2,151	6,356	6,323
Claims and claim adjustment expenses		1,241	1,118	3,620	3,378
Amortization of deferred acquisition costs		329	324	973	957
General and administrative expenses		312	309	923	909
Total claims and expenses		1,882	1,751	5,516	5,244
Income before income taxes		294	400	840	1,079
Income tax expense (benefit)		81	113	219	292
Net income		213	287	621	787
Total other-than-temporary impairment losses		(3)	(9)	(18)	(13)
Other-than-temporary impairment losses recognized in net realized investment gains (losses)		(3)	(9)	(13)	(12)
Other-than-temporary impairment gains (losses) recognized in other comprehensive income				(5)	(1)
TRV [Member]
Consolidating Statement of Income
Net investment income		3	1	9	4
Net realized investment gains (losses)					1
Total revenues		3	1	9	5
General and administrative expenses		4	4	9	12
Interest expense		78	82	238	242
Total claims and expenses		82	86	247	254
Income before income taxes		(79)	(85)	(238)	(249)
Income tax expense (benefit)		(44)	(27)	(123)	(76)
Net income of subsidiaries		751	986	2,186	2,746
Net income		716	928	2,071	2,573
Eliminations [Member]
Consolidating Statement of Income
Net realized investment gains (losses)		1		1
Other revenues		(4)		(18)
Total revenues		(3)		(17)
General and administrative expenses		(3)		(17)
Total claims and expenses		(3)		(17)
Net income of subsidiaries		(751)	(986)	(2,186)	(2,746)
Net income		$ (751)	$ (986)	$ (2,186)	$ (2,746)

[1] Total other-than-temporary impairment (OTTI) losses were $(4) million and $(14) million for the three months ended September 30, 2016 and 2015, respectively, and $(36) million and $(26) million for the nine months ended September 30, 2016 and 2015, respectively. Of total OTTI, credit losses of $(4) million and $(14) million for the three months ended September 30, 2016 and 2015, respectively, and $(26) million and $(23) million for the nine months ended September 30, 2016 and 2015, respectively, were recognized in net realized investment gains. In addition, unrealized gains (losses) from other changes in total OTTI of $0 million for both of the three months ended September 30, 2016 and 2015, and $(10) million and $(3) million for the nine months ended September 30, 2016 and 2015, respectively, were recognized in other comprehensive income (loss) as part of changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income.