Intangible Assets (Estimated Amortization Expense Over Next Five Years) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jan. 14, 2016
Finite-Lived Intangible Assets [Line Items]
Amortization of Purchased Intangibles	$ 19	$ 171	$ 108
Finite-Lived Intangible Assets, Net	3,800	$ 789
2017, Other intangible assets	251
2018, Other intangible assets	328
2019, Other intangible assets	286
2020, Other intangible assets	263
2021, Other intangible assets	249
Total, Other intangible assets	$ 1,377
Agency distribution relationships and renewal rights [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	24 years
Developed Technology Rights [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	3 years
Other Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
2017, Other intangible assets	$ 84
2018, Other intangible assets	74
2019, Other intangible assets	68
2020, Other intangible assets	59
2021, Other intangible assets	52
Total, Other intangible assets	337
The Chubb Corporation [Member]
Finite-Lived Intangible Assets [Line Items]
2017, Other intangible assets	167
2018, Other intangible assets	254
2019, Other intangible assets	218
2020, Other intangible assets	204
2021, Other intangible assets	197
Total, Other intangible assets	1,040
The Chubb Corporation [Member] | Agency distribution relationships and renewal rights [Member]
Finite-Lived Intangible Assets [Line Items]
2017, Other intangible assets	295
2018, Other intangible assets	323
2019, Other intangible assets	280
2020, Other intangible assets	239
2021, Other intangible assets	217
Total, Other intangible assets	1,354
The Chubb Corporation [Member] | Developed Technology Rights [Member]
Finite-Lived Intangible Assets [Line Items]
2017, Other intangible assets	32
2018, Other intangible assets	32
2019, Other intangible assets	0
2020, Other intangible assets	0
2021, Other intangible assets	0
Total, Other intangible assets	64
The Chubb Corporation [Member] | Fair Value Adjustment to Acquired Loss Reserves [Member]
Finite-Lived Intangible Assets [Line Items]
2017, Other intangible assets	(160)
2018, Other intangible assets	(101)
2019, Other intangible assets	(62)
2020, Other intangible assets	(35)
2021, Other intangible assets	(20)
Total, Other intangible assets	(378)
Increase Decrease on Acquired Unpaid Losses and Loss Expenses	$ 470			$ 715
Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	1 year
Minimum | The Chubb Corporation [Member] | Fair Value Adjustment to Acquired Loss Reserves [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	5 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	30 years
Maximum | The Chubb Corporation [Member] | Fair Value Adjustment to Acquired Loss Reserves [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	17 years