Commitments and Contingencies (Future Minimum Operating Lease Payments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Operating leases, rent expense, minimum rentals	$ 139	$ 131	$ 135
Real Estate Leases
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2016	100
2017	82
2018	63
2019	45
2020	26
Thereafter	44
Total	360
Non-Rental Equipment Leases
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2016	38
2017	36
2018	29
2019	23
2020	23
Thereafter	0
Total	$ 149