4. Equipment under operating leases, net:

The Company’s equipment under operating leases, net consists of the following (in thousands):


					Depreciation/
					Amortization
	Balance		Reclassifications		Expense or		Balance
	December 31,		Additions / Dispositions		Amortization		December 31,
	2018		and Impairment Losses		of Leases		2019
Equipment under operating leases, net	$	3,689	$	(967)	$	(130)	$	2,592
Assets held for sale or lease, net		1,188		8		—		1,196
Initial direct costs, net of accumulated amortization of $6 thousand and $3 thousand at December 31, 2019 and 2018, respectively		7		—		(3)		4
Total	$	4,884	$	(959)	$	(133)	$	3,792

During the respective years ended December 31, 2019 and 2018, the Company recorded $281 thousand and $459 thousand of impairment losses to reduce the fair value of certain equipment.

The Company utilizes a straight line depreciation method for equipment in all of the categories currently in its portfolio of operating lease transactions. Depreciation expense on the Company’s equipment was $130 thousand and $522 thousand for 2019 and 2018, respectively. IDC amortization expense related to operating leases totaled $3 thousand and $2 thousand for 2019 and 2018, respectively.

All of the leased property was acquired in the years beginning with 2005 through 2011.

As of December 31, 2019 and 2018, there were no lease contracts placed in non-accrual status. As of the same dates, the Company may have had certain other leases that have related accounts receivable aged 90 days or more that have not been placed on non-accrual status. In accordance with Company policy, such receivables are fully reserved. Management continues to closely monitor these leases, and all other lease contracts, for any actual change in collectability status and indication of necessary valuation adjustments.

Operating leases:

Property on operating leases consisted of the following (in thousands):


	Balance						Balance
	December 31,				Reclassification		December 31,
	2018		Additions		/Dispositions		2019
Transportation, rail	$	12,393	$	—	$	(243)	$	12,150
Trucks and Trailers		3,419		—		(3,336)		83
Aircraft		1,988		—		(256)		1,732
Manufacturing		624		—		—		624
Petro/natural gas		470		—		—		470
Materials handling		157		—		(26)		131
		19,051		—		(3,861)		15,190
Less accumulated depreciation		(15,362)		(130)		2,894		(12,598)
Total	$	3,689	$	(130)	$	(967)	$	2,592

The average estimated residual value for assets on operating leases was 17% and 19% of the assets’ original cost at December 31, 2019 and 2018, respectively. There were no operating lease in non-accrual status at December 31, 2019 and 2018.

At December 31, 2019, the aggregate amounts of future minimum lease payments receivable were as follows (in thousands):


	Operating
	Leases
Year Ending December 31, 2020		574
2021		273
2022		141
2023		80
2024		49
	$	1,117

The useful lives for each category of leases is reviewed at a minimum of once per quarter. As of December 31, 2019 and 2018, the respective useful lives of each category of lease assets in the Company’s portfolio were as follows (in years):


Equipment category		Useful Life
Transportation, rail		35 - 50
Aircraft		20 - 30
Manufacturing		10 - 15
Petro/natural gas		10 - 15
Materials handling		7 - 10
Transportation, other		7 - 10