Fair Value Measurement - Not Carried at Fair Value (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Assets:
Short-term investments	$ 720		$ 904
Other invested assets	134		170
Credit derivative assets	78		94
FG VIEs' assets, at fair value	1,257		2,565
Liabilities:
Credit derivative liabilities	2,001		1,787
FG VIEs' liabilities with recourse, at fair value	1,346		1,790
FG VIEs' liabilities without recourse, at fair value	101		1,081
Fair value measurement on recurring basis | Estimated Fair Value
Assets:
Fixed maturity securities	10,094		9,711
Short-term investments	720		904
Other invested assets	94	[1]	127	[1]
Credit derivative assets	78		94
FG VIEs' assets, at fair value	1,257		2,565
Other assets	77		84
Total assets carried at fair value	12,320		13,485
Liabilities:
Credit derivative liabilities	2,001		1,787
FG VIEs' liabilities with recourse, at fair value	1,346		1,790
FG VIEs' liabilities without recourse, at fair value	101		1,081
Total liabilities carried at fair value	3,448		4,658
Fair value measurement on recurring basis | Estimated Fair Value | Obligations of state and political subdivisions
Assets:
Fixed maturity securities	5,249		5,079
Fair value measurement on recurring basis | Estimated Fair Value | U.S. government and agencies
Assets:
Fixed maturity securities	701		700
Fair value measurement on recurring basis | Estimated Fair Value | Corporate securities
Assets:
Fixed maturity securities	1,427		1,340
Fair value measurement on recurring basis | Estimated Fair Value | RMBS
Assets:
Fixed maturity securities	1,171		1,122
Fair value measurement on recurring basis | Estimated Fair Value | CMBS
Assets:
Fixed maturity securities	670		549
Fair value measurement on recurring basis | Estimated Fair Value | Asset-backed securities
Assets:
Fixed maturity securities	554		608
Fair value measurement on recurring basis | Estimated Fair Value | Foreign government securities
Assets:
Fixed maturity securities	322		313
Fair value measurement on recurring basis | Level 1
Assets:
Fixed maturity securities	0		0
Short-term investments	438		506
Other invested assets	0	[1]	0	[1]
Credit derivative assets	0		0
FG VIEs' assets, at fair value	0		0
Other assets	29		27
Total assets carried at fair value	467		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	9,307		8,981
Short-term investments	282		398
Other invested assets	40	[1]	119	[1]
Credit derivative assets	0		0
FG VIEs' assets, at fair value	0		0
Other assets	11		11
Total assets carried at fair value	9,640		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	5,211		5,043
Fair value measurement on recurring basis | Level 2 | U.S. government and agencies
Assets:
Fixed maturity securities	701		700
Fair value measurement on recurring basis | Level 2 | Corporate securities
Assets:
Fixed maturity securities	1,289		1,204
Fair value measurement on recurring basis | Level 2 | RMBS
Assets:
Fixed maturity securities	812		832
Fair value measurement on recurring basis | Level 2 | CMBS
Assets:
Fixed maturity securities	670		549
Fair value measurement on recurring basis | Level 2 | Asset-backed securities
Assets:
Fixed maturity securities	302		340
Fair value measurement on recurring basis | Level 2 | Foreign government securities
Assets:
Fixed maturity securities	322		313
Fair value measurement on recurring basis | Level 3
Assets:
Fixed maturity securities	787		730
Short-term investments	0		0
Other invested assets	54	[1]	8	[1]
Credit derivative assets	78		94
FG VIEs' assets, at fair value	1,257		2,565
Other assets	37		46
Total assets carried at fair value	2,213		3,443
Liabilities:
Credit derivative liabilities	2,001		1,787
FG VIEs' liabilities with recourse, at fair value	1,346		1,790
FG VIEs' liabilities without recourse, at fair value	101		1,081
Total liabilities carried at fair value	3,448		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	138		136
Fair value measurement on recurring basis | Level 3 | RMBS
Assets:
Fixed maturity securities	359		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	252		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.