COMMITMENTS

Purchase Obligations and Lease Commitments

The Company had various purchase obligations at December 31, 2015 totaling $1.4 billion over a period of approximately 30 years for materials, supplies, and energy incident to the ordinary conduct of business. The Company also had various lease commitments for property and equipment under cancelable, noncancelable, and month-to-month operating leases totaling approximately $273 million over a period of approximately 40 years. Of the total lease commitments, approximately 50 percent relate to real property, including office space, storage facilities, and land; approximately 45 percent relate to railcars; and approximately 5 percent relate to machinery and equipment, including computer and communications equipment and production equipment. Rental expense, net of sublease income, was $91 million, $80 million, and $73 million in 2015, 2014, and 2013, respectively.

The obligations described above, debt repayment obligations, and credit facilities and commercial paper borrowings, are summarized in the following table:



(Dollars in millions)	Payments Due For
Period	Debt Securities		Credit Facilities and Other		Interest Payable		Purchase Obligations		Operating Leases		Total
2016	$	—	$	431	$	265	$	145	$	63	$	904
2017	999		1		283		164		50		1,497
2018	167		326		238		161		38		930
2019	250		226		218		148		28		870
2020	799		—		190		134		22		1,145
2021 and beyond	3,840		—		1,926		673		72		6,511
Total	$	6,055	$	984	$	3,120	$	1,425	$	273	$	11,857

Guarantees

The Company has operating leases with terms that require the Company to guarantee a portion of the residual value of the leased assets upon termination of the lease as well as other guarantees. Disclosures about each group of similar guarantees are provided below.

Residual Value Guarantees

The Company has operating leases with terms that require the Company to guarantee a portion of the residual value of the leased assets upon termination of the lease. These residual value guarantees at December 31, 2015 totaled $120 million and consisted primarily of leases for railcars and Company aircraft and will expire beginning in 2016. Management believes, based on current facts and circumstances, that the likelihood of material residual guarantee payments is remote.

Other Guarantees

Guarantees and claims also arise during the ordinary course of business from relationships with customers, suppliers, joint venture partners, and other parties when the Company undertakes an obligation to guarantee the performance of others, if specified triggering events occur. Non-performance under a contract could trigger an obligation of the Company. The Company's current other guarantees include guarantees relating primarily to intellectual property, environmental matters, and other indemnifications and have arisen through the normal course of business. The ultimate effect on future financial results is not subject to reasonable estimation because considerable uncertainty exists as to the final outcome of these claims, if they were to occur. These other guarantees have terms up to 30 years with maximum potential future payments of approximately $35 million in the aggregate, with none of these guarantees being individually significant to the Company's operating results, financial position, or liquidity. The Company's current expectation is that future payment or performance related to non-performance under other guarantees is considered remote.