Fair Value Measurement - Fair Value of Financial Instruments (Details) - USD ($) $ in Millions		Jun. 30, 2016	Dec. 31, 2015
Assets:
Fixed-maturity securities		$ 10,545	$ 11,023
Short-term investments		585	396
Other invested assets		170	169
Credit derivative assets		36	81
Liabilities:
Credit derivative liabilities		432	446
Investments not carried at fair value, carrying value		96	93
Carrying Amount [Member]
Assets:
Fixed-maturity securities		9,960	10,627
Short-term investments		585	396
Other invested assets	[1]	155	150
Credit derivative assets		36	81
FG VIEs’ assets, at fair value		814	1,261
Other assets		187	206
Liabilities:
Financial guaranty insurance contracts	[2]	3,690	3,998
Long-term debt		1,303	1,300
Credit derivative liabilities		432	446
FG VIEs’ liabilities with recourse, at fair value		790	1,225
FG VIEs’ liabilities without recourse, at fair value		115	124
Other liabilities		7	9
Estimated Fair Value [Member]
Assets:
Fixed-maturity securities		9,960	10,627
Short-term investments		585	396
Other invested assets	[1]	157	152
Credit derivative assets		36	81
FG VIEs’ assets, at fair value		814	1,261
Other assets		187	206
Liabilities:
Financial guaranty insurance contracts	[2]	9,928	8,712
Long-term debt		1,527	1,512
Credit derivative liabilities		432	446
FG VIEs’ liabilities with recourse, at fair value		790	1,225
FG VIEs’ liabilities without recourse, at fair value		115	124
Other liabilities		$ 7	$ 9

[1] Includes investments not carried at fair value with a carrying value of $96 million and $93 million as of June 30, 2016 and December 31, 2015, respectively. 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.