Fair Value Measurement - Fair Value of Financial Instruments (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Carrying amount and estimated fair value financial instruments
Other invested assets		$ 93
Assets:
Fixed-maturity securities		11,023	$ 11,258
Short-term investments		396	767
Other invested assets		169	126
Credit derivative assets		81	68
Liabilities:
Credit derivative liabilities		446	963
Carrying Amount [Member]
Assets:
Fixed-maturity securities		10,627	10,491
Short-term investments		396	767
Other invested assets	[1]	150	108
Credit derivative assets		81	68
FG VIEs’ assets, at fair value		1,261	1,398
Other assets		206	184
Liabilities:
Financial guaranty insurance contracts	[2]	3,998	3,823
Long-term debt		1,300	1,297
Credit derivative liabilities		446	963
FG VIEs’ liabilities with recourse, at fair value		1,225	1,277
FG VIEs’ liabilities without recourse, at fair value		124	142
Other liabilities		9	27
Estimated Fair Value [Member]
Assets:
Fixed-maturity securities		10,627	10,491
Short-term investments		396	767
Other invested assets	[1]	152	110
Credit derivative assets		81	68
FG VIEs’ assets, at fair value		1,261	1,398
Other assets		206	184
Liabilities:
Financial guaranty insurance contracts	[2]	8,712	6,205
Long-term debt		1,512	1,603
Credit derivative liabilities		446	963
FG VIEs’ liabilities with recourse, at fair value		1,225	1,277
FG VIEs’ liabilities without recourse, at fair value		124	142
Other liabilities		$ 9	$ 27

[1] Includes investments not carried at fair value with a carrying value of $93 million. Excludes investments carried under the equity method.

[2] Carrying amount includes the assets and liabilities related to financial guaranty insurance contract premiums, losses, and salvage and subrogation and other recoverables net of reinsurance.