Fair Value Measurements - Level 3 Financial Assets and Liabilities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Other asset and mortgage-backed securities [Member] Valued Using Pricing Models [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Other asset and mortgage-backed securities [Member] Valued Using Pricing Models [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Other asset and mortgage-backed securities [Member] Unobservable Inputs Developed By Company [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Other asset and mortgage-backed securities [Member] Unobservable Inputs Developed By Company [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Other asset and mortgage-backed securities [Member] Maximum [Member] Unobservable Inputs Developed By Company [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Other asset and mortgage-backed securities [Member] Maximum [Member] Unobservable Inputs Developed By Company [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Other asset and mortgage-backed securities [Member] Minimum [Member] Unobservable Inputs Developed By Company [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Other asset and mortgage-backed securities [Member] Minimum [Member] Unobservable Inputs Developed By Company [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Other asset and mortgage-backed securities [Member] Weighted Average [Member] Unobservable Inputs Developed By Company [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Other asset and mortgage-backed securities [Member] Weighted Average [Member] Unobservable Inputs Developed By Company [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Corporate and government debt securities [Member] Valued Using Pricing Models [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Corporate and government debt securities [Member] Valued Using Pricing Models [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Corporate and government debt securities [Member] Unobservable Inputs Developed By Company [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Corporate and government debt securities [Member] Unobservable Inputs Developed By Company [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Corporate and government debt securities [Member] Maximum [Member] Unobservable Inputs Developed By Company [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Corporate and government debt securities [Member] Maximum [Member] Unobservable Inputs Developed By Company [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Corporate and government debt securities [Member] Minimum [Member] Unobservable Inputs Developed By Company [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Corporate and government debt securities [Member] Minimum [Member] Unobservable Inputs Developed By Company [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Corporate and government debt securities [Member] Weighted Average [Member] Unobservable Inputs Developed By Company [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Corporate and government debt securities [Member] Weighted Average [Member] Unobservable Inputs Developed By Company [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Corporate [Member] Valued At Transaction Price [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Corporate [Member] Valued At Transaction Price [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Equity securities [Member] Valued At Transaction Price [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value Inputs Level 3 [Member] Equity securities [Member] Valued At Transaction Price [Member]
Fair Value Disclosures [Abstract]
Percentage of investments in fixed maturities and equity securities classified in Level 3	7.00%
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fixed Maturities And Equity Securities		$ 16,627	$ 17,816	$ 1,190	$ 1,351	$ 603	$ 598	$ 593	$ 584							$ 417	$ 596	$ 305	$ 439							$ 111	$ 123	$ 59	$ 34
Liquidity adjustment to discount rates used to value fixed maturities and equity securities										6.20%	4.10%	0.60%	0.60%	1.70%	1.40%					3.70%	6.40%	0.80%	0.20%	2.00%	1.90%
Adjustment to discount rates used to value fixed maturities and equity securities for weighting of credit spreads										20.90%	45.40%	1.20%	0.50%	2.90%	4.10%
Percentage of fixed maturities classified in Level 3 that represent single, unadjusted, non-binding broker quotes	10.00%
Percentage of Level 3 securities valued at transaction price	15.00%