Shareholders' Equity and Dividend Availability (details) - Dividend Availability $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) item $ / shares	Dec. 31, 2014 USD ($) item $ / shares	Dec. 31, 2013 USD ($) item $ / shares
Statutory accounting principals
Dividends received by TRV and its two non-insurance holding companies from their U.S. insurance subsidiaries	$ 3,750	$ 4,100	$ 2,900
Cash dividends declared per common share | $ / shares	$ 2.38	$ 2.15	$ 1.96
Cash dividends paid	$ 739	$ 729	$ 729
Insurance subsidiaries [Member]
Statutory accounting principals
Statutory net income of the Company's domestic and international insurance subsidiaries	3,800	3,970	$ 4,180
Statutory capital and surplus of the Company's domestic and international insurance subsidiaries	$ 20,570	$ 21,050
Travelers [Member]
Statutory accounting principals
Number of non-insurance holding companies underneath TRV | item	2	2	2
Cash dividends declared per common share | $ / shares	$ 2.38	$ 2.15	$ 1.96
Cash dividends paid	$ 739	$ 729	$ 729
Connecticut Insurance Department [Member] | Insurance subsidiaries [Member]
Statutory accounting principals
Maximum amount of dividends available to be paid by subsidiaries to their parent without prior approval of the Connecticut Insurance Department	$ 3,810