Guarantees and Commitments (Guarantees to third parties) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Guarantor Obligations [Line Items]
Standby letters of credit and other guarantees	$ 7	$ 8
Standby letters of credit, cash collateral received	2
Maximum
Guarantor Obligations [Line Items]
Standby letters of credit and other guarantees	$ 218	$ 227