Guarantees and Commitments Guarantees and Commitments (Guarantees to third parties) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Guarantor Obligations [Line Items]
Standby letters of credit and other guarantees	$ 8	$ 8
Maximum [Member]
Guarantor Obligations [Line Items]
Standby letters of credit and other guarantees	$ 227	$ 175

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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