Summary of Significant Accounting Policies (Details 2) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Securities loaned
Cash collateral received as percentage of fair value of domestic securities loaned	102.00%
Cash collateral received as a percent of fair value of foreign securities loaned	105.00%
Deferred Policy Acquisition and Sales Inducement Costs
Valuation allowance for uncollectible premium installment receivables	$ 84	$ 90
Present value of future profits	53	58
Amortization expense of present value of future profits	$ 5	$ 8	$ 13
Minimum
Deferred Policy Acquisition and Sales Inducement Costs
Property-liability policies, term for deferment and recognition of premiums	6 months
Period for amortization of DAC for property-liability insurance	6 months
Period for amortization of DAC and DSI for interest-sensitive life, fixed annuities and other investment contracts	15 years
Maximum
Securities loaned
Securities lending transactions length	30 days
Deferred Policy Acquisition and Sales Inducement Costs
Property-liability policies, term for deferment and recognition of premiums	12 months
Period for amortization of DAC for property-liability insurance	12 months
Period for amortization of DAC and DSI for interest-sensitive life, fixed annuities and other investment contracts	30 years
Interest-sensitive life insurance | Minimum
Deferred Policy Acquisition and Sales Inducement Costs
Period for amortization of DAC and DSI for interest-sensitive life, fixed annuities and other investment contracts	10 years
Interest-sensitive life insurance | Maximum
Deferred Policy Acquisition and Sales Inducement Costs
Period for amortization of DAC and DSI for interest-sensitive life, fixed annuities and other investment contracts	20 years
Fixed annuities | Minimum
Deferred Policy Acquisition and Sales Inducement Costs
Period for amortization of DAC and DSI for interest-sensitive life, fixed annuities and other investment contracts	5 years
Fixed annuities | Maximum
Deferred Policy Acquisition and Sales Inducement Costs
Period for amortization of DAC and DSI for interest-sensitive life, fixed annuities and other investment contracts	10 years