12. Lease Obligations

From time to time, the Company enters into leasing arrangements for real estate, vehicles and construction equipment. In 2017, the Company entered into master leasing arrangements for vehicles and construction equipment. Some of the leases entered into under these agreements met the requirements for capitalizations and were recorded as capital leases, while others were treated as operating leases. As of December 31, 2017, the Company had no outstanding commitments to enter into future leases under its master lease agreements.

Capital Leases

The Company leases vehicles and certain equipment under capital leases. The economic substance of the leases is a financing transaction for acquisition of the vehicles and equipment and, accordingly, the leases are included in the balance sheets in property and equipment, net of accumulated depreciation, with a corresponding amount recorded in current portion of capital lease obligations or capital lease obligations, net of current maturities, as appropriate. The capital lease assets are amortized on a straight-line basis over the life of the lease or, if shorter, the life of the leased asset, and included in depreciation expense in the statements of operations. The interest associated with capital leases is included in interest expense in the statements of operations.

As of December 31, 2017, the Company had approximately $3.7 million of capital lease obligations outstanding, $1.1 million of which was classified as a current liability.

As of December 31, 2017 and 2016, $3.7 million and $5.0 million, respectively, of leased assets were capitalized in construction equipment, net of accumulated depreciation. Additional information related to property and equipment is provided in Note 6 — Property and Equipment to the Financial Statements.

Operating Leases

The Company leases real estate, construction equipment and office equipment under operating leases with remaining terms ranging from one to six years.

Rent expense includes lease payments as well as rent on items that are rented under cancellable rental agreements. Total rent expense for the years ended December 31, 2017, 2016 and 2015, was $44.6 million, $44.9 million and $57.2 million, respectively.

The future minimum lease payments required under capital leases, together with their present value of capital leases, and operating leases as of December 31, 2017 were as follows:

(In thousands)	Capital Lease Obligations			Operating Lease Obligations
2018	$	1,185		$	3,599
2019		1,185			2,885
2020		1,185			2,187
2021		360			1,582
2022		—			1,014
Thereafter		—			564
Total minimum lease payments	$	3,915		$	11,831
Interest		(200	)
Net present of minimum lease payments		3,715
Less: Current portion of capital lease obligations		1,086
Long-term capital lease obligations	$	2,629