Contracts Accounted for as Insurance - Gross Premium Receivable Net of Commissions on Assumed Business Roll Forward (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Gross Premium Receivable Net of Ceding Commissions [Roll Forward]
Beginning balance	$ 915	$ 576
Less: Non-financial guaranty insurance premium receivable	1	0
FG insurance premiums receivable	914	576
Premiums receivable from acquisitions (see Note 2)	0	270
Gross written premiums on new business, net of commissions (2)	75	110
Gross premiums received, net of commissions	(63)	(92)
Adjustments:
Changes in the expected term	(3)	(1)
Accretion of discount, net of commissions on assumed business	(4)	4
Foreign exchange translation	24	9
FG insurance premiums receivable	943	876
Non-financial guaranty insurance premium receivable	1	0
Ending balance	944	876
Variable Interest Entity, Primary Beneficiary [Member]
Adjustments:
Ending balance	$ 9	$ 11