Consolidating Financial Statements (details) - Consolidating Statement of Income (Unaudited) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Consolidating Statement of Income
Premiums		$ 6,067	$ 5,931	$ 12,048	$ 11,819
Net investment income		549	632	1,093	1,224
Fee income		119	115	236	229
Net realized investment gains (losses)	[1]	19	10	10	20
Other revenues		31	22	84	47
Total revenues		6,785	6,710	13,471	13,339
Claims and claim adjustment expenses		3,762	3,547	7,474	6,978
Amortization of deferred acquisition costs		989	963	1,960	1,926
General and administrative expenses		1,054	1,032	2,049	2,027
Interest expense		93	92	184	184
Total claims and expenses		5,898	5,634	11,667	11,115
Income before income taxes		887	1,076	1,804	2,224
Income tax expense (benefit)		223	264	449	579
Net income		664	812	1,355	1,645
Total other-than-temporary impairment losses		(4)	(8)	(32)	(12)
Other-than-temporary impairment losses recognized in net realized investment gains (losses)		(4)	(6)	(22)	(9)
Other-than-temporary impairment gains (losses) recognized in other comprehensive income		0	(2)	(10)	(3)
TPC [Member]
Consolidating Statement of Income
Premiums		4,161	4,044	8,246	8,040
Net investment income		377	424	753	835
Fee income		119	115	236	229
Net realized investment gains (losses)		(1)	17	(17)	19
Other revenues		33	19	81	40
Total revenues		4,689	4,619	9,299	9,163
Claims and claim adjustment expenses		2,575	2,409	5,095	4,718
Amortization of deferred acquisition costs		666	651	1,316	1,293
General and administrative expenses		743	721	1,447	1,419
Interest expense		12	12	24	24
Total claims and expenses		3,996	3,793	7,882	7,454
Income before income taxes		693	826	1,417	1,709
Income tax expense (benefit)		191	198	390	449
Net income		502	628	1,027	1,260
Total other-than-temporary impairment losses		(3)	(7)	(17)	(8)
Other-than-temporary impairment losses recognized in net realized investment gains (losses)		(3)	(5)	(12)	(6)
Other-than-temporary impairment gains (losses) recognized in other comprehensive income			(2)	(5)	(2)
Other Subsidiaries [Member]
Consolidating Statement of Income
Premiums		1,906	1,887	3,802	3,779
Net investment income		168	206	334	386
Net realized investment gains (losses)		20	(7)	27
Other revenues		1	3	17	7
Total revenues		2,095	2,089	4,180	4,172
Claims and claim adjustment expenses		1,187	1,138	2,379	2,260
Amortization of deferred acquisition costs		323	312	644	633
General and administrative expenses		313	308	611	600
Total claims and expenses		1,823	1,758	3,634	3,493
Income before income taxes		272	331	546	679
Income tax expense (benefit)		69	86	138	179
Net income		203	245	408	500
Total other-than-temporary impairment losses		(1)	(1)	(15)	(4)
Other-than-temporary impairment losses recognized in net realized investment gains (losses)		(1)	(1)	(10)	(3)
Other-than-temporary impairment gains (losses) recognized in other comprehensive income				(5)	(1)
TRV [Member]
Consolidating Statement of Income
Net investment income		4	2	6	3
Net realized investment gains (losses)					1
Total revenues		4	2	6	4
General and administrative expenses		1	3	5	8
Interest expense		81	80	160	160
Total claims and expenses		82	83	165	168
Income before income taxes		(78)	(81)	(159)	(164)
Income tax expense (benefit)		(37)	(20)	(79)	(49)
Net income of subsidiaries		705	873	1,435	1,760
Net income		664	812	1,355	1,645
Eliminations [Member]
Consolidating Statement of Income
Other revenues		(3)		(14)
Total revenues		(3)		(14)
General and administrative expenses		(3)		(14)
Total claims and expenses		(3)		(14)
Net income of subsidiaries		(705)	(873)	(1,435)	(1,760)
Net income		$ (705)	$ (873)	$ (1,435)	$ (1,760)

[1] Total other-than-temporary impairment (OTTI) losses were $(4) million and $(8) million for the three months ended June 30, 2016 and 2015, respectively, and $(32) million and $(12) million for the six months ended June 30, 2016 and 2015, respectively. Of total OTTI, credit losses of $(4) million and $(6) million for the three months ended June 30, 2016 and 2015, respectively, and $(22) million and $(9) million for the six months ended June 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 and $(2) million for the three months ended June 30, 2016 and 2015, respectively, and $(10) million and $(3) million for the six months ended June 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.