Borrowings and Contractual Commitments Contractual Commitments (Additional Information) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Long-term Purchase Commitment [Line Items]
Minimum Termination Fee for Contractual Commitments	$ 5
Amount paid during period related to purchase obligations	395	$ 236	$ 243
time deposits $250,000 or more	$ 3,200	$ 1,700

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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