Outstanding Exposure Outstanding Exposure - Schedule of Non-Financial Guaranty Exposure (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Capital relieve triple-X life insurance [Member]
Schedule of Insured Financial Obligations [Line Items]
Gross Exposure	$ 883	$ 773
Net Exposure	766	675
Aircraft residual value insurance policies [Member]
Schedule of Insured Financial Obligations [Line Items]
Gross Exposure	340	201
Net Exposure	$ 218	$ 140