Debt (Schedule of Debt Outstanding) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Repurchase Agreements	$ 1,403	$ 1,404
Short-term debt	500	0
Long-term debt	12,636	9,389
Trust preferred securities	308	307
Senior Notes [Member]
Debt Instrument [Line Items]
Long-term debt	12,636	9,389
Senior Notes [Member] | ACE INA Senior Notes Due February 2017 [Member]
Debt Instrument [Line Items]
Short-term debt	$ 500	0
Interest Rate	5.70%
Long-term debt	$ 0	500
Make Whole Premium Additional Percent	0.20%
Senior Notes [Member] | ACE INA Senior Notes Due March 2018 [Member]
Debt Instrument [Line Items]
Interest Rate	5.80%
Long-term debt	$ 299	299
Make Whole Premium Additional Percent	0.35%
Senior Notes [Member] | Chubb INA Senior Notes Due May 2018 [Member]
Debt Instrument [Line Items]
Interest Rate	5.75%
Long-term debt	$ 654	0
Make Whole Premium Additional Percent	0.30%
Senior Notes [Member] | ACE INA Senior Notes Due June 2019 [Member]
Debt Instrument [Line Items]
Interest Rate	5.90%
Long-term debt	$ 497	497
Make Whole Premium Additional Percent	0.40%
Senior Notes [Member] | ACE INA senior notes due 2020 [Member]
Debt Instrument [Line Items]
Interest Rate	2.30%
Long-term debt	$ 1,293	1,294
Make Whole Premium Additional Percent	0.15%
Senior Notes [Member] | ACE INA senior notes due 2022 [Member]
Debt Instrument [Line Items]
Interest Rate	2.875%
Long-term debt	$ 993	994
Make Whole Premium Additional Percent	0.20%
Senior Notes [Member] | ACE INA Senior Notes Due March 2023 [Member]
Debt Instrument [Line Items]
Interest Rate	2.70%
Long-term debt	$ 471	471
Make Whole Premium Additional Percent	0.10%
Senior Notes [Member] | ACE INA Senior Notes Due May 2024 [Member]
Debt Instrument [Line Items]
Interest Rate	3.35%
Long-term debt	$ 694	694
Make Whole Premium Additional Percent	0.15%
Senior Notes [Member] | ACE INA senior notes due 2025 [Member]
Debt Instrument [Line Items]
Interest Rate	3.15%
Long-term debt	$ 794	794
Make Whole Premium Additional Percent	0.15%
Senior Notes [Member] | ACE INA senior notes due 2026 [Member]
Debt Instrument [Line Items]
Interest Rate	3.35%
Long-term debt	$ 1,487	1,487
Make Whole Premium Additional Percent	0.20%
Senior Notes [Member] | ACE INA Senior Notes Due May 2036 [Member]
Debt Instrument [Line Items]
Interest Rate	6.70%
Long-term debt	$ 297	297
Make Whole Premium Additional Percent	0.20%
Senior Notes [Member] | Chubb INA Senior Notes Due 2037 [Member]
Debt Instrument [Line Items]
Interest Rate	6.00%
Long-term debt	$ 992	0
Make Whole Premium Additional Percent	0.20%
Senior Notes [Member] | Chubb INA Senior Notes Due 2038 [Member]
Debt Instrument [Line Items]
Interest Rate	6.50%
Long-term debt	$ 784	0
Make Whole Premium Additional Percent	0.30%
Senior Notes [Member] | ACE INA Senior Notes Due March 2043 [Member]
Debt Instrument [Line Items]
Interest Rate	4.15%
Long-term debt	$ 469	469
Make Whole Premium Additional Percent	0.15%
Senior Notes [Member] | ACE INA senior notes due 2045 [Member]
Debt Instrument [Line Items]
Interest Rate	4.35%
Long-term debt	$ 1,482	1,482
Make Whole Premium Additional Percent	0.25%
Senior Notes [Member] | Pennsylvania Industrial Development Authority (PIDA) AND City Of Philadelphia Urban Development Action Grant [Member]
Debt Instrument [Line Items]
Long-term debt	$ 11	11
Junior Subordinated Debt [Member] | Chubb INA Capital Securities Due 2067 [Member]
Debt Instrument [Line Items]
Interest Rate	6.375%
Long-term debt	$ 948
Debentures Subject to Mandatory Redemption [Member] | Chubb INA Senior Notes Due August 2018 [Member]
Debt Instrument [Line Items]
Interest Rate	6.60%
Long-term debt	$ 111
Debentures Subject to Mandatory Redemption [Member] | ACE INA Senior Notes Due August 2029 [Member]
Debt Instrument [Line Items]
Interest Rate	8.875%
Long-term debt	$ 100	100
Unsecured Debt [Member] | Chubb INA Senior Notes Due 2031 [Member]
Debt Instrument [Line Items]
Interest Rate	6.80%
Long-term debt	$ 260
Make Whole Premium Additional Percent	0.25%
Trust Preferred Securities [Member] | ACE INA Capital Securities Due 2030 [Member]
Debt Instrument [Line Items]
Trust preferred securities	$ 308	307
Repurchase Agreements [Member]
Debt Instrument [Line Items]
Repurchase Agreements	$ 1,403	$ 1,404
Short-term Debt, Weighted Average Interest Rate	0.80%	0.60%
Minimum [Member] | Senior Notes [Member] | Pennsylvania Industrial Development Authority (PIDA) AND City Of Philadelphia Urban Development Action Grant [Member]
Debt Instrument [Line Items]
Interest Rate	2.75%
Minimum [Member] | Junior Subordinated Debt [Member] | Chubb INA Capital Securities Due 2067 [Member]
Debt Instrument [Line Items]
Make Whole Premium Additional Percent	0.25%
Maximum [Member] | Senior Notes [Member] | Pennsylvania Industrial Development Authority (PIDA) AND City Of Philadelphia Urban Development Action Grant [Member]
Debt Instrument [Line Items]
Interest Rate	7.10%
Maximum [Member] | Junior Subordinated Debt [Member] | Chubb INA Capital Securities Due 2067 [Member]
Debt Instrument [Line Items]
Make Whole Premium Additional Percent	0.50%