Statutory Financial Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statutory Accounting Practices [Line Items]
Dividends available to be paid	$ 3,700
Approximate increase in statutory capital and surplus resulting from discount of certain A&E liabilities	155	$ 144
Minimum statutory capital and surplus required to satisfy regulatory requirements	22,800	14,500
Statutory Accounting Practices, Permitted Practice, Amount	308
PropertyAndCasualtySubsidiaries [Member]
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	37,946	19,680
Statutory net income	7,042	2,712	$ 3,378
LifeSubsidiaries [Member] [Member]
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	1,294	1,207
Statutory net income	$ 46	$ (148)	$ (248)