Schedule II Schedule II (STATEMENTS OF OPERATIONS - Parent Company Only) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Financial Statements, Captions [Line Items]
Equity in net income of subsidiaries and affiliates									$ 514	$ 418	$ 264
Total revenues	$ 7,626	$ 8,750	$ 8,510	$ 7,831	$ 8,015	$ 8,610	$ 8,108	$ 7,510	32,717	32,243	31,469
Administrative and other (income) expense									2,886	2,833	3,081
Business Combination, Integration Related Costs									59	310	492
Income tax expense (benefit)									695	(139)	815
Total expenses									28,060	28,521	26,519
Net income	$ 355	$ 1,231	$ 1,294	$ 1,082	$ 1,533	$ (70)	$ 1,305	$ 1,093	3,962	3,861	4,135
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest									1,242
Chubb limited (Parent Guarantor)
Condensed Financial Statements, Captions [Line Items]
Investment income, including intercompany interest income									305	336	356
Equity in net income of subsidiaries and affiliates									3,753	3,640	3,901
Total revenues									4,058	3,976	4,257
Administrative and other (income) expense									63	63	39
Business Combination, Integration Related Costs									14	32	62
Income tax expense (benefit)									19	20	21
Total expenses									96	115	122
Net income									3,962	3,861	4,135
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest									$ 1,242	$ 4,718	$ 4,556