Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Lease Payments for Capital and Operating Leases [Table Text Block]

Future minimum lease payments as of December 31, 2018, are summarized as follows (in millions):

December 31,	Capital Leases			Operating Leasesa
2019	$	72		$	400
2020	69			496
2021	200			421
2022	35			328
2023	28			289
Thereafter	101			787
Total	505			$	2,721
Less amount representing interest	(86		)
Present value of minimum lease payments	$	419

^a Excludes leases having non-cancelable lease terms of less than one year and per diem leases. Minimum lease payments have not been reduced by minimum sublease rentals of $131 million due under future non-cancelable subleases.

Schedule of Loss Contingencies by Contingency

The following table summarizes the activity in the Company’s accrued obligations for personal injury matters (in millions):

	Year Ended			Year Ended			Year Ended
	December 31, 2018			December 31, 2017			December 31, 2016
Beginning balance	$	307		$	367		$	375
Accruals / changes in estimates	76			(1		)	80
Payments	(75		)	(59		)	(88		)
Ending balance	$	308		$	307		$	367

Accrued Obligations for Environmental Matters

The following table summarizes the activity in the Company’s accrued obligations for environmental matters (in millions):

	Year Ended			Year Ended			Year Ended
	December 31, 2018			December 31, 2017			December 31, 2016
Beginning balance	$	317		$	342		$	369
Accruals / changes in estimates	—			5			5
Payments	(19		)	(30		)	(32		)
Ending balance	$	298		$	317		$	342