Schedule II (details) - Condensed Balance Sheets - USD ($) shares in Millions, $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Balance Sheet
Fixed maturities, at fair value	$ 62,694	$ 60,515
Equity securities	453	732
Short-term securities	4,895	4,865
Total assets	103,483	100,245
Debt	6,571	6,437
Total liabilities	79,752	77,024
Common stock (1,750.0 shares authorized; 271.5 and 279.6 shares issued and 271.4 and 279.6 shares outstanding)	22,886	22,614
Retained earnings	33,462	32,196
Accumulated other comprehensive loss	(343)	(755)
Treasury stock, at cost (500.9 and 489.5 shares)	(32,274)	(30,834)
Total shareholders' equity	23,731	23,221	$ 23,598
Total liabilities and shareholders' equity	$ 103,483	$ 100,245
Common stock, shares authorized (in shares)	1,750.0	1,750.0
Common stock, shares issued (in shares)	271.5	279.6
Common stock, shares outstanding (in shares)	271.4	279.6
Treasury stock, at cost (in shares)	500.9	489.5
Travelers [Member]
Condensed Balance Sheet
Fixed maturities, at fair value	$ 82	$ 49
Equity securities	181	155
Short-term securities	1,230	1,627
Investment in subsidiaries	27,946	27,137
Other assets	692	68
Total assets	30,131	29,036
Debt	5,878	5,744
Other liabilities	524	82
Total liabilities	6,402	5,826
Common stock (1,750.0 shares authorized; 271.5 and 279.6 shares issued and 271.4 and 279.6 shares outstanding)	22,886	22,614
Retained earnings	33,460	32,185
Accumulated other comprehensive loss	(343)	(755)
Treasury stock, at cost (500.9 and 489.5 shares)	(32,274)	(30,834)
Total shareholders' equity	23,729	23,210
Total liabilities and shareholders' equity	$ 30,131	$ 29,036
Common stock, shares authorized (in shares)	1,750.0	1,750.0
Common stock, shares issued (in shares)	271.5	279.6
Common stock, shares outstanding (in shares)	271.4	279.6
Treasury stock, at cost (in shares)	500.9	489.5