3. Balance Sheet Details

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


	June 30,		March 31,
	2018		2019
Accounts receivable	$	225,336	$	234,411
Less allowance for doubtful accounts		(14,592)		(15,978)
Total	$	210,744	$	218,433


	June 30,		March 31,
	2018		2019
Raw materials	$	156,612	$	151,383
Work-in-process		89,468		79,188
Finished goods		67,472		67,133
Total	$	313,552	$	297,704


	June 30,		March 31,
	2018		2019
Land	$	16,569	$	16,561
Buildings, civil works and improvements		56,585		55,322
Leasehold improvements		9,681		7,903
Equipment and tooling		117,294		127,579
Furniture and fixtures		3,331		3,202
Computer equipment		18,759		18,199
Computer software		19,509		19,647
Computer software implementation in process		4,318		7,747
Construction in process		790		4,682
Total		246,836		260,842
Less accumulated depreciation and amortization		(131,312)		(135,926)
Property and equipment, net	$	115,524	$	124,916

Depreciation expense was $5.4 million and $5.1 million for the three months ended March 31, 2018 and 2019, respectively, and approximately $38.4 million and $15.4 million for the nine months ended March 31, 2018 and 2019, respectively. The year-over-year decrease in depreciation for the nine months ended March 31, 2019 is due to certain assets becoming fully depreciated in fiscal year 2018, as well as the transfer of certain assets as discussed below.

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 and nine months ended March 31, 2019, we recognized $3.6 million and $10.7 million, respectively, of amortization expense related to such assets. For the three and nine months ended March 31, 2018, we recognized $3.2 million of amortization expense related to such assets. As of March 31, 2019, $11.1 million was recorded within Prepaid expenses and other current assets.