Consolidating Financial Statements (Details) - Consolidating Statement of Income (Unaudited) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Consolidating Statement of Income
Premiums										$ 28,272	$ 27,059	$ 25,683
Net investment income										2,468	2,474	2,397
Fee income										459	432	447
Net realized investment gains (losses)	[1]									113	114	216
Other revenues										269	203	159
Total revenues		$ 8,063	$ 8,013	$ 7,834	$ 7,671	$ 7,796	$ 7,723	$ 7,477	$ 7,286	31,581	30,282	28,902
Claims and claim adjustment expenses										19,133	18,291	17,467
Amortization of deferred acquisition costs										4,601	4,381	4,166
General and administrative expenses										4,365	4,297	4,170
Interest expense										344	352	369
Total claims and expenses		6,989	7,581	7,169	6,704	7,050	6,917	6,846	6,508	28,443	27,321	26,172
Income before income taxes		1,074	432	665	967	746	806	631	778	3,138	2,961	2,730
Income tax expense (benefit)		201	36	108	171	125	97	107	109	516	438	674
Net income of subsidiaries										0	0	0
Net income		$ 873	$ 396	$ 557	$ 796	$ 621	$ 709	$ 524	$ 669	2,622	2,523	2,056
Total other-than-temporary impairment losses										(3)	(1)	(13)
Other-than-temporary impairment losses recognized in net realized investment gains (losses)										(4)	(1)
Other-than-temporary impairment losses recognized in net realized investment gains (losses)												(14)
Other-than-temporary impairment losses recognized in other comprehensive income (loss)											0
Other-than-temporary impairment gains recognized in other comprehensive income (loss)										1		1
TRV [Member]
Consolidating Statement of Income
Net investment income										41	32	24
Net realized investment gains (losses)										33	(13)	66
Total revenues										74	19	90
General and administrative expenses										21	20	25
Interest expense										297	304	321
Total claims and expenses										318	324	346
Income before income taxes										(244)	(305)	(256)
Income tax expense (benefit)										(77)	(114)	(130)
Net income of subsidiaries										2,789	2,714	2,190
Net income										2,622	2,523	2,064
Other-than-temporary impairment losses recognized in net realized investment gains (losses)										0	0
Other-than-temporary impairment losses recognized in net realized investment gains (losses)												0
Other-than-temporary impairment losses recognized in other comprehensive income (loss)											0
Other-than-temporary impairment gains recognized in other comprehensive income (loss)										0		0
Reportable Legal Entities [Member] | TPC [Member]
Consolidating Statement of Income
Premiums										19,362	18,508	17,562
Net investment income										1,730	1,704	1,627
Fee income										458	432	447
Net realized investment gains (losses)										44	118	19
Other revenues										142	96	101
Total revenues										21,736	20,858	19,756
Claims and claim adjustment expenses										12,926	12,344	11,735
Amortization of deferred acquisition costs										3,095	2,972	2,820
General and administrative expenses										2,973	2,947	2,906
Interest expense										47	48	48
Total claims and expenses										19,041	18,311	17,509
Income before income taxes										2,695	2,547	2,247
Income tax expense (benefit)										483	437	519
Net income of subsidiaries										0	0	0
Net income										2,212	2,110	1,728
Total other-than-temporary impairment losses										(2)	(1)	(4)
Other-than-temporary impairment losses recognized in net realized investment gains (losses)										(2)	(1)
Other-than-temporary impairment losses recognized in net realized investment gains (losses)												(5)
Other-than-temporary impairment losses recognized in other comprehensive income (loss)											0
Other-than-temporary impairment gains recognized in other comprehensive income (loss)										0		1
Reportable Legal Entities [Member] | Other Subsidiaries [Member]
Consolidating Statement of Income
Premiums										8,910	8,551	8,121
Net investment income										697	738	759
Fee income										1	0	0
Net realized investment gains (losses)										36	9	131
Other revenues										127	112	68
Total revenues										9,771	9,410	9,079
Claims and claim adjustment expenses										6,207	5,947	5,732
Amortization of deferred acquisition costs										1,506	1,409	1,346
General and administrative expenses										1,371	1,335	1,249
Interest expense										0	0	0
Total claims and expenses										9,084	8,691	8,327
Income before income taxes										687	719	752
Income tax expense (benefit)										110	115	290
Net income of subsidiaries										0	0	0
Net income										577	604	462
Total other-than-temporary impairment losses										(1)	0	(9)
Other-than-temporary impairment losses recognized in net realized investment gains (losses)										(2)	0
Other-than-temporary impairment losses recognized in net realized investment gains (losses)												(9)
Other-than-temporary impairment losses recognized in other comprehensive income (loss)											0
Other-than-temporary impairment gains recognized in other comprehensive income (loss)										1		0
Reportable Legal Entities [Member] | TRV [Member]
Consolidating Statement of Income
Premiums										0	0	0
Net investment income										41	32	24
Fee income										0	0	0
Net realized investment gains (losses)										33	(13)	66
Other revenues										0	0	0
Total revenues										74	19	90
Claims and claim adjustment expenses										0	0	0
Amortization of deferred acquisition costs										0	0	0
General and administrative expenses										21	20	25
Interest expense										297	304	321
Total claims and expenses										318	324	346
Income before income taxes										(244)	(305)	(256)
Income tax expense (benefit)										(77)	(114)	(130)
Net income of subsidiaries										2,789	2,714	2,190
Net income										2,622	2,523	2,064
Total other-than-temporary impairment losses										0	0	0
Other-than-temporary impairment losses recognized in net realized investment gains (losses)										0	0
Other-than-temporary impairment losses recognized in net realized investment gains (losses)												0
Other-than-temporary impairment losses recognized in other comprehensive income (loss)											0
Other-than-temporary impairment gains recognized in other comprehensive income (loss)										0		0
Eliminations [Member]
Consolidating Statement of Income
Premiums										0	0	0
Net investment income										0	0	(13)
Fee income										0	0	0
Net realized investment gains (losses)										0	0	0
Other revenues										0	(5)	(10)
Total revenues										0	(5)	(23)
Claims and claim adjustment expenses										0	0	0
Amortization of deferred acquisition costs										0	0	0
General and administrative expenses										0	(5)	(10)
Interest expense										0	0	0
Total claims and expenses										0	(5)	(10)
Income before income taxes										0	0	(13)
Income tax expense (benefit)										0	0	(5)
Net income of subsidiaries										(2,789)	(2,714)	(2,190)
Net income										(2,789)	(2,714)	(2,198)
Total other-than-temporary impairment losses										0	0	0
Other-than-temporary impairment losses recognized in net realized investment gains (losses)										0	0
Other-than-temporary impairment losses recognized in net realized investment gains (losses)												0
Other-than-temporary impairment losses recognized in other comprehensive income (loss)											$ 0
Other-than-temporary impairment gains recognized in other comprehensive income (loss)										$ 0		$ 0

[1] Total other-than-temporary impairment (OTTI) losses were $(3) million, $(1) million and $(13) million for the years ended December 31, 2019, 2018 and 2017, respectively.  Of total OTTI, credit losses of $(4) million, $(1) million and $(14) million for the years ended December 31, 2019, 2018 and 2017, respectively, were recognized in net realized investment gains.  In addition, unrealized gains (losses) from other changes in total OTTI of $1 million, $0 million and $1 million for the years ended December 31, 2019, 2018 and 2017, respectively, were recognized in other comprehensive income (loss) as part of changes in net unrealized gains (losses) on investment securities having credit losses recognized in the consolidated statement of income.