Contracts Accounted for as Insurance - Gross Premium Receivable Net of Commissions on Assumed Business Roll Forward (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Gross Premium Receivable Net of Ceding Commissions [Roll Forward]
December 31,	$ 576	$ 693
Premiums receivable from acquisitions (see Note 2)	270	0
Gross written premiums on new business, net of commissions on assumed business	179	83
Gross premiums received, net of commissions on assumed business	(159)	(107)
Adjustments:
Changes in the expected term	0	(27)
Accretion of discount, net of commissions on assumed business	9	3
Foreign exchange translation	35	(22)
June 30 - financial guaranty	910	623
Other	6	0
June 30,	916	623
Variable Interest Entity, Primary Beneficiary [Member]
Adjustments:
June 30,	$ 10	$ 11