Consolidating Financial Statements (Details) - Consolidating Statement of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Consolidating Statement of Cash Flows
Net income	$ 557	$ 524	$ 1,353	$ 1,193
Net adjustments to reconcile net income to net cash provided by operating activities			439	505
Net cash provided by operating activities			1,792	1,698
Proceeds from maturities of fixed maturities			3,038	3,657
Proceeds from sales of investments:
Fixed maturities			1,495	2,607
Equity securities			71	92
Other investments			240	189
Purchases of investments:
Fixed maturities			(5,708)	(7,952)
Equity securities			(41)	(60)
Real estate investments			(85)	(44)
Other investments			(262)	(275)
Net sales (purchases) of short-term securities			497	1,202
Securities transactions in course of settlement			223	279
Other investing activities			(169)	(152)
Net cash used in investing activities			(701)	(457)
Treasury stock acquired — share repurchase authorization			(750)	(700)
Treasury stock acquired — net employee share-based compensation			(47)	(51)
Dividends paid to shareholders			(419)	(404)
Payment of debt			(500)	(600)
Issuance of debt			492	491
Issuance of common stock — employee share options			174	98
Dividends paid to parent company			0	0
Net cash used in financing activities			(1,050)	(1,166)
Effect of exchange rate changes on cash			2	(4)
Net increase in cash			43	71
Cash at beginning of year			373	344
Cash at end of period	416	415	416	415
Income taxes paid (received)			325	238
Interest paid			171	175
Reportable Legal Entities [Member] | TPC [Member]
Consolidating Statement of Cash Flows
Net income	512	458	1,137	1,009
Net adjustments to reconcile net income to net cash provided by operating activities			314	323
Net cash provided by operating activities			1,451	1,332
Proceeds from maturities of fixed maturities			2,106	2,730
Proceeds from sales of investments:
Fixed maturities			968	1,847
Equity securities			33	33
Other investments			201	133
Purchases of investments:
Fixed maturities			(4,049)	(5,762)
Equity securities			(1)	(2)
Real estate investments			0	0
Other investments			(234)	(232)
Net sales (purchases) of short-term securities			416	986
Securities transactions in course of settlement			157	268
Other investing activities			(166)	(148)
Net cash used in investing activities			(569)	(147)
Treasury stock acquired — share repurchase authorization			0	0
Treasury stock acquired — net employee share-based compensation			0	0
Dividends paid to shareholders			0	0
Payment of debt			0	0
Issuance of debt			0	0
Issuance of common stock — employee share options			0	0
Dividends paid to parent company			(866)	(1,109)
Net cash used in financing activities			(866)	(1,109)
Effect of exchange rate changes on cash			1	(2)
Net increase in cash			17	74
Cash at beginning of year			181	157
Cash at end of period	198	231	198	231
Income taxes paid (received)			244	193
Interest paid			24	24
Reportable Legal Entities [Member] | Other Subsidiaries [Member]
Consolidating Statement of Cash Flows
Net income	84	120	292	288
Net adjustments to reconcile net income to net cash provided by operating activities			213	11
Net cash provided by operating activities			505	299
Proceeds from maturities of fixed maturities			924	914
Proceeds from sales of investments:
Fixed maturities			526	759
Equity securities			38	59
Other investments			39	56
Purchases of investments:
Fixed maturities			(1,650)	(2,173)
Equity securities			(37)	(56)
Real estate investments			(85)	(44)
Other investments			(28)	(43)
Net sales (purchases) of short-term securities			125	383
Securities transactions in course of settlement			66	12
Other investing activities			(3)	(4)
Net cash used in investing activities			(85)	(137)
Treasury stock acquired — share repurchase authorization			0	0
Treasury stock acquired — net employee share-based compensation			0	0
Dividends paid to shareholders			0	0
Payment of debt			(32)	0
Issuance of debt			0	7
Issuance of common stock — employee share options			0	0
Dividends paid to parent company			(363)	(170)
Net cash used in financing activities			(395)	(163)
Effect of exchange rate changes on cash			1	(2)
Net increase in cash			26	(3)
Cash at beginning of year			192	187
Cash at end of period	218	184	218	184
Income taxes paid (received)			91	171
Interest paid			0	0
Reportable Legal Entities [Member] | TRV [Member]
Consolidating Statement of Cash Flows
Net income	557	524	1,353	1,193
Net adjustments to reconcile net income to net cash provided by operating activities			(256)	146
Net cash provided by operating activities			1,097	1,339
Proceeds from maturities of fixed maturities			8	13
Proceeds from sales of investments:
Fixed maturities			1	1
Equity securities			0	0
Other investments			0	0
Purchases of investments:
Fixed maturities			(9)	(17)
Equity securities			(3)	(2)
Real estate investments			0	0
Other investments			0	0
Net sales (purchases) of short-term securities			(44)	(167)
Securities transactions in course of settlement			0	(1)
Other investing activities			0	0
Net cash used in investing activities			(47)	(173)
Treasury stock acquired — share repurchase authorization			(750)	(700)
Treasury stock acquired — net employee share-based compensation			(47)	(51)
Dividends paid to shareholders			(419)	(404)
Payment of debt			(500)	(600)
Issuance of debt			492	491
Issuance of common stock — employee share options			174	98
Dividends paid to parent company			0	0
Net cash used in financing activities			(1,050)	(1,166)
Effect of exchange rate changes on cash			0	0
Net increase in cash			0	0
Cash at beginning of year			0	0
Cash at end of period	0	0	0	0
Income taxes paid (received)			(10)	(126)
Interest paid			147	151
Eliminations [Member]
Consolidating Statement of Cash Flows
Net income	(596)	(578)	(1,429)	(1,297)
Net adjustments to reconcile net income to net cash provided by operating activities			168	25
Net cash provided by operating activities			(1,261)	(1,272)
Proceeds from maturities of fixed maturities			0	0
Proceeds from sales of investments:
Fixed maturities			0	0
Equity securities			0	0
Other investments			0	0
Purchases of investments:
Fixed maturities			0	0
Equity securities			0	0
Real estate investments			0	0
Other investments			0	0
Net sales (purchases) of short-term securities			0	0
Securities transactions in course of settlement			0	0
Other investing activities			0	0
Net cash used in investing activities			0	0
Treasury stock acquired — share repurchase authorization			0	0
Treasury stock acquired — net employee share-based compensation			0	0
Dividends paid to shareholders			0	0
Payment of debt			32	0
Issuance of debt			0	(7)
Issuance of common stock — employee share options			0	0
Dividends paid to parent company			1,229	1,279
Net cash used in financing activities			1,261	1,272
Effect of exchange rate changes on cash			0	0
Net increase in cash			0	0
Cash at beginning of year			0	0
Cash at end of period	$ 0	$ 0	0	0
Income taxes paid (received)			0	0
Interest paid			$ 0	$ 0