Outstanding Exposure Outstanding Exposure - Schedule of Non-Financial Guaranty Exposure (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Life Insurance Transaction [Member]
Schedule of Insured Financial Obligations [Line Items]
Gross Exposure	$ 912	$ 880
Net Exposure	788	763
Aircraft residual value insurance policies [Member]
Schedule of Insured Financial Obligations [Line Items]
Gross Exposure	360	340
Net Exposure	$ 239	$ 218