Fair Value Measurement - Measured and Carried at Fair Value (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended			9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended																9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2014 Security	Jun. 30, 2014	Dec. 31, 2013	Sep. 30, 2014 Minimum	Dec. 31, 2013 Minimum	Sep. 30, 2014 Maximum	Dec. 31, 2013 Maximum	Sep. 30, 2014 CDS contracts source		Dec. 31, 2013 CDS contracts		Sep. 30, 2014 CDS contracts Based on actual collateral specific spreads		Dec. 31, 2013 CDS contracts Based on actual collateral specific spreads		Sep. 30, 2014 CDS contracts Based on market indices		Dec. 31, 2013 CDS contracts Based on market indices		Sep. 30, 2014 CDS contracts Provided by the CDS counterparty		Dec. 31, 2013 CDS contracts Provided by the CDS counterparty		Sep. 30, 2014 CDS contracts Minimum	Dec. 31, 2013 CDS contracts Minimum	Sep. 30, 2014 CDS contracts Maximum	Dec. 31, 2013 CDS contracts Maximum	Sep. 30, 2014 Scenario 1 CDS contracts	Sep. 30, 2014 Scenario 1 CDS contracts AGC	Sep. 30, 2014 Scenario 2 CDS contracts	Sep. 30, 2014 Scenario 2 CDS contracts AGC	Sep. 30, 2014 Level 3 Fair value measurement on recurring basis	Dec. 31, 2013 Level 3 Fair value measurement on recurring basis	Sep. 30, 2014 Level 2 Fair value measurement on recurring basis	Dec. 31, 2013 Level 2 Fair value measurement on recurring basis
Credit Derivatives
Number of fixed maturity securities valued using model processes	42
Percentage of fixed maturity securities valued using model processes to the Company's fixed-income securities and short-term investments at fair value	8.10%
Fixed maturity securities																																$ 913	$ 730	$ 9,572	$ 8,981
Other investments																																		$ 93
Discount factor (as a percent)				0.00%	0.00%	3.68%	4.44%																	0.15%	0.21%	3.18%	3.88%
Gross spread percentage								100.00%	[1]	100.00%	[1]	8.00%	[1]	6.00%	[1]	84.00%	[1]	88.00%	[1]	8.00%	[1]	6.00%	[1]
Number of sources of credit spread								3
Percentage of CDS contracts which are fair valued using minimum premium	58.00%	28.00%	61.00%
Original gross spread/cash bond price (as a percent)																												1.85%		5.00%
Bank profit (as a percent)																												1.15%		0.50%
Hedge cost (as a percent)																												0.30%		4.40%
The Company premium received per annum (as a percent)																												0.40%		0.10%
Bank profit as % of total																												62.00%		10.00%
Hedge cost as % of total																												16.00%		88.00%
Premium received per annum as % of total																												22.00%		2.00%
Percentage of exposure hedged																													10.00%		25.00%

[1] Based on par.