The Company has various operating leases primarily for equipment, delivery centers and office space, which generally contain renewal options. Rent expense under operating leases was approximately $33.2 million, $33.3 million and $33.1 million for the years ended December 31, 2014, 2013 and 2012, respectively.

In 2008, the Company sub-leased one of its delivery centers to a third party for the remaining term of the original lease. The sub-lease began on January 1, 2009 and rental income is recognized on a straight-line basis over the term of the sub-lease through 2021. Future minimum sub-lease rental receipts are shown in the table below.

The future minimum rental payments and receipts required under non-cancelable operating leases as of December 31, 2014 are as follows (in thousands):

			Operating Leases		Sub-Lease Income
2015		$	43,411	$	(2,234)
2016			34,248		(2,234)
2017			26,505		(2,234)
2018			18,582		(2,470)
2019			9,665		(2,470)
Thereafter			3,826		(2,675)
	Total	$	136,237	$	(14,317)

The Company records operating lease expense on a straight-line basis over the life of the lease as described in Note 1. The deferred lease liability as of December 31, 2014 and 2013 was $9.0 million and $9.6 million, respectively.

The Company records asset retirement obligations (“ARO”) for its delivery center leases. Capitalized costs related to ARO's are included in Other long-term assets in the accompanying Consolidated Balance Sheets while the ARO liability is included in Other long-term liabilities in the accompanying Consolidated Balance Sheets. Following is a summary of the amounts recorded (in thousands):

		Balance at December 31, 2013		Additions and Modifications		Accretion		Settlements		Balance at December 31, 2014

ARO liability total	$	1,888	$	39	$	14	$	-	$	1,941

		Balance at December 31, 2012		Additions and Modifications		Accretion		Settlements		Balance at December 31, 2013

ARO liability total	$	2,061	$	-	$	42	$	(215)	$	1,888

Increases to ARO result from a new lease agreement or modifications on an ARO from a preexisting lease agreement. Modifications to ARO liabilities and accumulated accretion occur when lease agreements are amended or when assumptions change, such as the rate of inflation. Modifications are accounted for prospectively as changes in estimates. Settlements occur when leased premises are vacated and the actual cost of restoration is paid. Differences between the actual costs of restoration and the balance recorded as ARO liabilities are recognized as gains or losses in the accompanying Consolidated Statements of Comprehensive Income (Loss).