Commitments, Guarantees and Contingencies Aggregate Minimum Rentals (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
2017		$ 69
2018		58
2019		48
2020		35
2021		27
Thereafter		78
Total	[1]	315
Operating lease expense		$ 84	$ 59	$ 67

[1] Minimum payments have not been reduced by minimum sublease rentals due in the future under noncancelable subleases.