Fair Value Measurement - Carried at Fair Value (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Assets:
Short-term investments	$ 837		$ 904
Other invested assets	127		170
Credit derivative assets	86		94
FG VIEs' assets, at fair value	1,296		2,565
Liabilities:
Credit derivative liabilities	1,654		1,787
FG VIEs' liabilities with recourse, at fair value	1,326		1,790
FG VIEs' liabilities without recourse, at fair value	133		1,081
Fair value measurement on recurring basis | Estimated Fair Value
Assets:
Fixed maturity securities	10,485		9,711
Short-term investments	837		904
Other invested assets	99	[1]	127	[1]
Credit derivative assets	86		94
FG VIEs' assets, at fair value	1,296		2,565
Other assets	77		84
Total assets carried at fair value	12,880		13,485
Liabilities:
Credit derivative liabilities	1,654		1,787
FG VIEs' liabilities with recourse, at fair value	1,326		1,790
FG VIEs' liabilities without recourse, at fair value	133		1,081
Total liabilities carried at fair value	3,113		4,658
Fair value measurement on recurring basis | Estimated Fair Value | Obligations of state and political subdivisions
Assets:
Fixed maturity securities	5,615		5,079
Fair value measurement on recurring basis | Estimated Fair Value | U.S. government and agencies
Assets:
Fixed maturity securities	560		700
Fair value measurement on recurring basis | Estimated Fair Value | Corporate securities
Assets:
Fixed maturity securities	1,380		1,340
Fair value measurement on recurring basis | Estimated Fair Value | RMBS
Assets:
Fixed maturity securities	1,416		1,122
Fair value measurement on recurring basis | Estimated Fair Value | CMBS
Assets:
Fixed maturity securities	703		549
Fair value measurement on recurring basis | Estimated Fair Value | Asset-backed securities
Assets:
Fixed maturity securities	501		608
Fair value measurement on recurring basis | Estimated Fair Value | Foreign government securities
Assets:
Fixed maturity securities	310		313
Fair value measurement on recurring basis | Level 1
Assets:
Fixed maturity securities	0		0
Short-term investments	465		506
Other invested assets	0	[1]	0	[1]
Credit derivative assets	0		0
FG VIEs' assets, at fair value	0		0
Other assets	25		27
Total assets carried at fair value	490		533
Liabilities:
Credit derivative liabilities	0		0
FG VIEs' liabilities with recourse, at fair value	0		0
FG VIEs' liabilities without recourse, at fair value	0		0
Total liabilities carried at fair value	0		0
Fair value measurement on recurring basis | Level 1 | Obligations of state and political subdivisions
Assets:
Fixed maturity securities	0		0
Fair value measurement on recurring basis | Level 1 | U.S. government and agencies
Assets:
Fixed maturity securities	0		0
Fair value measurement on recurring basis | Level 1 | Corporate securities
Assets:
Fixed maturity securities	0		0
Fair value measurement on recurring basis | Level 1 | RMBS
Assets:
Fixed maturity securities	0		0
Fair value measurement on recurring basis | Level 1 | CMBS
Assets:
Fixed maturity securities	0		0
Fair value measurement on recurring basis | Level 1 | Asset-backed securities
Assets:
Fixed maturity securities	0		0
Fair value measurement on recurring basis | Level 1 | Foreign government securities
Assets:
Fixed maturity securities	0		0
Fair value measurement on recurring basis | Level 2
Assets:
Fixed maturity securities	9,572		8,981
Short-term investments	372		398
Other invested assets	17	[1]	119	[1]
Credit derivative assets	0		0
FG VIEs' assets, at fair value	0		0
Other assets	17		11
Total assets carried at fair value	9,978		9,509
Liabilities:
Credit derivative liabilities	0		0
FG VIEs' liabilities with recourse, at fair value	0		0
FG VIEs' liabilities without recourse, at fair value	0		0
Total liabilities carried at fair value	0		0
Fair value measurement on recurring basis | Level 2 | Obligations of state and political subdivisions
Assets:
Fixed maturity securities	5,577		5,043
Fair value measurement on recurring basis | Level 2 | U.S. government and agencies
Assets:
Fixed maturity securities	560		700
Fair value measurement on recurring basis | Level 2 | Corporate securities
Assets:
Fixed maturity securities	1,283		1,204
Fair value measurement on recurring basis | Level 2 | RMBS
Assets:
Fixed maturity securities	904		832
Fair value measurement on recurring basis | Level 2 | CMBS
Assets:
Fixed maturity securities	703		549
Fair value measurement on recurring basis | Level 2 | Asset-backed securities
Assets:
Fixed maturity securities	235		340
Fair value measurement on recurring basis | Level 2 | Foreign government securities
Assets:
Fixed maturity securities	310		313
Fair value measurement on recurring basis | Level 3
Assets:
Fixed maturity securities	913		730
Short-term investments	0		0
Other invested assets	82	[1]	8	[1]
Credit derivative assets	86		94
FG VIEs' assets, at fair value	1,296		2,565
Other assets	35		46
Total assets carried at fair value	2,412		3,443
Liabilities:
Credit derivative liabilities	1,654		1,787
FG VIEs' liabilities with recourse, at fair value	1,326		1,790
FG VIEs' liabilities without recourse, at fair value	133		1,081
Total liabilities carried at fair value	3,113		4,658
Fair value measurement on recurring basis | Level 3 | Obligations of state and political subdivisions
Assets:
Fixed maturity securities	38		36
Fair value measurement on recurring basis | Level 3 | U.S. government and agencies
Assets:
Fixed maturity securities	0		0
Fair value measurement on recurring basis | Level 3 | Corporate securities
Assets:
Fixed maturity securities	97		136
Fair value measurement on recurring basis | Level 3 | RMBS
Assets:
Fixed maturity securities	512		290
Fair value measurement on recurring basis | Level 3 | CMBS
Assets:
Fixed maturity securities	0		0
Fair value measurement on recurring basis | Level 3 | Asset-backed securities
Assets:
Fixed maturity securities	266		268
Fair value measurement on recurring basis | Level 3 | Foreign government securities
Assets:
Fixed maturity securities	$ 0		$ 0

[1] Includes Level 3 mortgage loans that are recorded at fair value on a non-recurring basis.