We are the subject of, or party to, a number of pending or threatened legal actions and claims arising in the ordinary course of our business including, but not limited to, royalty claims, contract claims and environmental claims. While many of these matters involve inherent uncertainty, we believe that the amount of the liability, if any, ultimately incurred with respect to proceedings or claims will not have a material adverse effect on our consolidated financial position as a whole or on our liquidity, capital resources or future annual results of operations. We will continue to evaluate our litigation on a quarterly basis and will establish and adjust any litigation reserves as appropriate to reflect our assessment of the then current status of litigation.

When deemed necessary, we established reserves for certain legal proceedings. The establishment of a reserve is based on an estimation process that include the advice of legal counsel and subjective judgment of management. While management believes these reserves to be adequate, it is reasonably possible we could incur additional losses with respect to those matters in which reserves have been established.

We lease office space, office equipment, production facilities, compressors and transportation equipment under cancelable and non-cancelable leases. We have subleased part of the office space included in our operating leases for which we receive rental payments. Rent expense under operating leases (including renewable monthly leases) totaled $19.3 million in 2018 compared to $19.1 million in 2017 and $14.0 million in 2016. Commitments related to these lease payments are not recorded in the accompanying consolidated balance sheets. Future minimum rental commitments under non-cancelable leases having remaining lease terms in excess of one year are as follows (in thousands):

	Operating Lease Obligations		Sublease Rental Receipts
2019	$	14,669	$	1,876
2020		14,080		1,696
2021		11,801		1,334
2022		7,217		111
2023		6,747		—
Thereafter		22,001		—
	$	76,515	$	5,017

We have entered into firm transportation and gathering contracts with various pipeline carriers for the future transportation and gathering of natural gas, NGLs and oil production from our properties in Pennsylvania and North Louisiana. Under these contracts, we are obligated to transport, process or gather minimum daily natural gas volumes, or pay for any deficiencies at a specified reservation fee rate. In most cases, our production committed to these pipelines is expected to exceed the minimum daily volumes provided in the contracts. As of December 31, 2018, future minimum transportation, processing and gathering fees under our commitments are as follows (in thousands):

	Transportation, Gathering and Processing Contracts ^(a)
2019	$	960,000
2020		905,162
2021		878,205
2022		834,506
2023		798,629
Thereafter		5,854,692
	$	10,231,194

^(a) The amounts in this table represent the gross amounts that we are committed to pay; however, we will record in our financial statements our proportionate share of costs based on our working interest which can vary based on volumes produced.

In addition to the amounts included in the above table, we have entered into additional agreements which are contingent on certain pipeline modifications and/or construction. The largest agreement has a ten-year term and is expected to begin in 2019. Based on this contract, we will have additional gathering obligations for natural gas volumes of 350,000 mcf per day until 2029. We also have an agreement which has a five-year term, which is expected to begin in 2020, for additional NGLs transportation of 20,000 bbls per day until March 2025.

We have various volume delivery commitments that are related to our Marcellus Shale and North Louisiana areas. We expect to be able to fulfill our contractual obligations from our own production; however, we may purchase third-party volumes to satisfy our commitments or pay demand fees for commitment shortfalls, should they occur. As of December 31, 2018, our delivery commitments through 2031 were as follows:

Year Ending December 31,	Natural Gas (mmbtu per day)		Ethane and Propane (bbls per day)
2019		347,935	74,000
2020		292,845	71,492
2021		138,011	55,932
2022		83,535	43,000
2023		2,628	35,000
2024—2028		—	35,000
2029—2031		—	20,000

In addition to the amounts included in the above table, we have contracted with a pipeline company through 2035 to deliver ethane production volumes from our Marcellus Shale wells. These agreements and related fees, which are contingent upon pipeline construction and/or modification, are for 3,000 bbls per day starting in 2021 and increasing to 10,000 bbls per day through 2035. In addition, we have agreements in place to deliver natural gas volumes from our Marcellus Shale wells, which are also contingent upon pipeline construction and/or modification, for 215,000 mcf per day starting in late 2020, decreasing to 151,000 mcf per day in 2024 and decreasing to 100,000 mcf per day in 2026 through early 2029.

We also have lease acreage that is generally subject to expiration if initial wells are not drilled within a specified period, generally between three and five years. We do not expect to lose significant lease acreage because of failure to drill due to inadequate capital, equipment or personnel. However, based on our evaluation of prospective economics, we have allowed acreage to expire and will allow additional acreage to expire in the future. To date, our expenditures to comply with environmental or safety regulations have not been a significant component of our cost structure and are not expected to be significant in the future. However, new regulations, enforcement policies, claims for damages or other events could result in significant future costs.