Borrowings and Contractual Commitments Contractual Commitments (Additional Information) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Long-term Purchase Commitment [Line Items]
Minimum Termination Fee for Contractual Commitments	$ 5
Amount paid during period related to purchase obligations	236	$ 243	$ 223
time deposits $250,000 or more	$ 1,700	$ 1,400