Consolidated Statements Of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities
Net income	$ 1,082	$ 1,093
Adjustments to reconcile net income to net cash flows from operating activities
Net realized (gains) losses	2	7
Amortization of premiums/discounts on fixed maturities	155	184
Amortization of UPR related to the Chubb Corp acquisition and other intangibles	85	64
Deferred income taxes	(2)	(127)
Unpaid losses and loss expenses	(420)	(154)
Unearned premiums	111	17
Future policy benefits	58	40
Insurance and reinsurance balances payable	250	252
Accounts payable, accrued expenses, and other liabilities	(724)	(491)
Income taxes payable	88	191
Insurance and reinsurance balances receivable	(174)	30
Reinsurance recoverable on losses and loss expenses	138	(122)
Reinsurance recoverable on policy benefits	3	(5)
Deferred policy acquisition costs	(75)	(59)
Prepaid reinsurance premiums	(42)	(81)
Other	16	174
Net cash flows from operating activities	551	1,013
Cash flows from investing activities
Purchases of fixed maturities available for sale	(5,972)	(6,250)
Purchases of fixed maturities held to maturity	(162)	(157)
Purchases of equity securities	(55)	(37)
Sales of fixed maturities available for sale	2,562	3,395
Sales of equity securities	40	46
Maturities and redemptions of fixed maturities available for sale	1,865	2,543
Maturities and redemptions of fixed maturities held to maturity	255	240
Net change in short-term investments	731	232
Net derivative instruments settlements	39	(89)
Private equity contribution	(353)	(198)
Private equity distribution	201	315
Other	(32)	(106)
Net cash flows used for investing activities	(881)	(66)
Cash flows from financing activities
Dividends paid on Common Shares	(330)	(324)
Common Shares repurchased	(29)	(128)
Proceeds from issuance of long-term debt	(300)	(500)
Proceeds from issuance of repurchase agreements	408	753
Proceeds from Issuance of Long-term Debt	2,175	0
Repayment of repurchase agreements	(404)	(752)
Proceeds from share-based compensation plans	34	42
Policyholder contract deposits	118	109
Policyholder contract withdrawals	(105)	(58)
Net cash flows from (used for) financing activities	1,567	(858)
Effect of foreign currency rate changes on cash and restricted cash	25	(17)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect	1,262	72
Cash and Restricted Cash - Beginning of year	851	1,088
Cash and Restricted Cash - end of Year	2,113	1,160
Supplemental cash flow information
Taxes paid	93	54
Interest paid	$ 82	$ 75