We lease certain equipment, office space and land. ROU assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As most of our leases do not provide an implicit rate, we use our incremental borrowing rate, which is derived from information available at the lease commencement date, in determining the present value of lease payments. We consider our recent debt issuances as well as publicly available data for instruments with similar characteristics when calculating our incremental borrowing rates. Most leases include one or more options to renew, with renewal terms that can extend the lease term between one to five years. The exercise of lease renewal options is at our sole discretion. Lease expense for lease payments is recognized on a straight-line basis over the lease term. Leases with an initial term of 12 months or less are not recorded on the balance sheet; we recognize lease expense for these leases on a straight-line basis over the lease term. Finance leases at March 31, 2019 were insignificant.

For certain equipment leases, we apply a portfolio approach to effectively account for the operating lease ROU assets and liabilities. For certain equipment leases, such as vehicles, we account for the lease and non-lease components as a single lease component. Certain leases also include options to purchase the leased equipment. The depreciable life of assets and leasehold improvements are limited by the expected lease term, unless there is a transfer of title or purchase option reasonably certain of exercise. Certain of our lease agreements include rental payments adjusted periodically for inflation. Our lease agreements do not contain any material residual value guarantees or material restrictive covenants and we do not have any significant sublease income.

(in thousands)	Classification	March 31, 2019
Assets
Operating lease assets	Other long-term assets	$	12,927

Liabilities
Current operating lease liability	Accounts payable and accrued liabilities	$	4,443
Noncurrent operating lease liability	Other long-term obligations		8,500
Total lease liabilities		$	12,943

(in thousands)	March 31, 2019
Lease costs¹	$	1,410
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	1,522
Leased assets exchanged for new operating lease liabilities	$	268
Weighted-average remaining terms (years)		3.63
Weighted-average discount rate		4.14	%

¹	Excludes short-term leases and variable lease costs, which are immaterial.

At March 31, 2019, the future minimum lease payment obligations under noncancelable operating leases were as follows:

(in thousands)
2019	$	3,707
2020		4,212
2021		3,200
2022		1,564
2023		668
After 2023		575
Total lease payments		13,926
Less: interest²		983
Present value of lease liabilities	$	12,943

¹	Operating lease payments include any options to extend lease terms that are reasonably certain of being exercised and excludes $8.2 million of legally binding agreements for property and equipment that we expect will be subject to operating lease agreements upon receipt and acceptance by us.

²	Calculated using the interest rate for each lease.

We did not have any capital leases during 2018. Operating lease rent expense primarily for office space, machinery and equipment was $1.2 million for the three months ended March 31, 2018.

At December 31, 2018, future minimum lease payment obligations under noncancelable operating leases were as follows:

(in thousands)
2019	$	5,130
2020		4,135
2021		3,142
2022		1,538
2023		629
2024 and thereafter		575
Total	$	15,149