Commitments And Contingencies Operating Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Rent Expense	$ 100	$ 85	$ 82
Operating Leases, Minimum Lease Commitments	$ 447