3. Balance Sheet Details

The following tables provide details of selected balance sheet accounts (in thousands):


	June 30,		September 30,
	2018		2018
Accounts receivable	$	221,240	$	233,778
Less allowance for doubtful accounts		(10,496)		(11,608)
Total	$	210,744	$	222,170


	June 30,		September 30,
	2018		2018
Raw materials	$	156,612	$	168,807
Work-in-process		89,468		89,095
Finished goods		67,472		86,072
Total	$	313,552	$	343,974


	June 30,		September 30,
	2018		2018
Land	$	16,569	$	16,569
Buildings, civil works and improvements		56,585		56,533
Leasehold improvements		9,681		9,772
Equipment and tooling		117,294		123,317
Furniture and fixtures		3,331		3,341
Computer equipment		18,759		19,229
Computer software		19,509		19,665
Computer software implementation in process		4,318		5,256
Construction in process		790		1,203
Total		246,836		254,885
Less accumulated depreciation and amortization		(131,312)		(135,121)
Property and equipment, net	$	115,524	$	119,764

Depreciation expense was $16.2 million and $5.1 million for the three months ended September 30, 2017 and 2018, respectively. The decrease in depreciation is primarily related to a transfer of assets.

In January 2018, we entered into a two-year agreement with the Mexican government to continue providing security screening services. Upon inception of the contract, we transferred certain fixed assets with a net book value of $29.5 million to the customer, and this remaining cost to obtain the contract is amortized on a straightline basis over the term of the contract as corresponding revenues are recognized. During the three months ended September 30, 2018, we recognized $3.7 million of amortization expense related to such assets. As of September 30, 2018, $14.7 million and $4.2 million are recorded within Prepaid expenses and other current assets and Other assets, respectively.