Commitments and Other Contingencies

We are committed under various operating lease agreements primarily related to office space and equipment. Generally, these leases include renewal provisions and rental payments, which may be adjusted for taxes, insurance and maintenance related to the property. Future minimum commitments under noncancellable operating leases are as follows (dollars in millions):



2018	$	176
2019	112
2020	69
2021	52
2022	32
Thereafter	192
	$	633

Total rent expense incurred under operating leases was approximately $217 million, $324 million and $426 million for the years ended December 31, 2017, 2016 and 2015, respectively. The future rental commitment table above does not include leases that are short-term in nature or can be cancelled with notice of less than three months.

Other Contingencies

The contractual residual value guarantee balance of of $28 million in “Other Non-Current Liabilities” on the accompanying Consolidated Balance Sheets at December 31, 2016 was extinguished after the underlying leased equipment in our North America pressure pumping operations was purchased during the first quarter of 2017.

We have minimum purchase commitments related to supply contracts and maintain a liability at December 31, 2017 of $69 million for expected penalties to be paid, of which $22 million is recorded in “Other Current Liabilities” and $47 million is recorded in “Other Non-Current Liabilities” on our Consolidated Balance Sheets.