Commitments and Contingencies (Future Minimum Operating Lease Payments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Operating leases, rent expense, minimum rentals	$ 149	$ 139	$ 131
Real Estate Leases
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2017	99
2018	82
2019	63
2020	44
2021	28
Thereafter	39
Total	355
Non-Rental Equipment Leases
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2017	41
2018	30
2019	22
2020	15
2021	8
Thereafter	2
Total	$ 118