Balance Sheet Components

Short-Term Marketable Securities

Our Short-term marketable securities consisted of U.S. government agency obligations with maturities up to two years, which we carried at their fair value as Level 1 instruments in accordance with ASC 820, "Fair Value Measurements." We liquidated these investments in the first quarter of fiscal 2019. The following table summarizes the maturities of our formerly-held Short-term marketable securities at fair value.



(In thousands)	December 28, 2019		December 29, 2018
Short-term marketable securities:
Maturing within one year	$	—	$	7,454
Maturing between one and two years	—		2,170
Total marketable securities	$	—	$	9,624

Accounts Receivable

Accounts receivable do not bear interest and are shown net of allowances for doubtful accounts. The allowance for doubtful accounts reflects our best estimate of probable losses inherent in the accounts receivable balance. We determine the allowance based on assessment of known troubled accounts, analysis of the aging of our accounts receivable, historical experience, management judgment, and other currently available evidence.



(In thousands)	December 28, 2019			December 29, 2018
Accounts receivable	$	65,023		$	61,087
Less: Allowance for doubtful accounts	(106		)	(197		)
Accounts receivable, net of allowance for doubtful accounts	$	64,917		$	60,890

The following table displays the activity related to changes in our allowance for doubtful accounts:



Fiscal Years Ended (In thousands)	Balance at beginning of period		Charged (Credit) to costs and expenses			Charged (credit) to other accounts			Settlements & write-offs net of recoveries			Balance at end of period
Allowance for doubtful accounts
December 28, 2019	$	197	$	(30	)	$	(12	)	$	(49	)	$	106
December 29, 2018	$	9,371	$	1		$	73		$	(9,248	)	$	197
December 30, 2017	$	9,299	$	3		$	38		$	31		$	9,371

During fiscal 2018, we wrote off $9.0 million of accounts receivable from a bankrupt distributor group. This write off had no impact on Accounts Receivable in fiscal 2018, as we had recorded a full allowance against our accounts receivable, net of deferred revenue, from the bankrupt distributor group in fiscal 2016.

Inventories



(In thousands)	December 28, 2019		December 29, 2018
Work in progress	$	39,855	$	47,224
Finished goods	15,125		19,872
Total inventories	$	54,980	$	67,096

In the second quarter of 2018, we made the strategic decision to discontinue our millimeter wave business, which included certain wireless technology inventory items. As such, specific inventory charges of $8.0 million were taken during fiscal 2018 on product lines eliminated with the discontinuation of our millimeter wave business and were charged to Cost of revenue in the Consolidated Statements of Operations.

Accounts Payable and Accrued Expenses

Included in Accounts payable and accrued expenses in the Consolidated Balance Sheets are the following balances:



(In thousands)	December 28, 2019		December 29, 2018
Trade accounts payable	$	44,350	$	31,880
Liability for non-cancelable contracts	6,964		6,078
Restructuring	3,060		4,220
Other accrued expenses	5,881		9,585
Total accounts payable and accrued expenses	$	60,255	$	51,763

Cloud Based Computing Implementation Costs

During the fourth quarter of fiscal 2019, we early adopted ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40), which clarifies the accounting for implementation costs in cloud computing arrangements. We adopted this guidance using the retrospective method, but did not restate any prior financial statements presented. As of December 28, 2019, we had capitalized approximately $2.5 million of implementation costs mainly for our new and interrelated distributor accounting management systems. These cloud based computing implementation costs are recorded in Prepaid expenses and other current assets and Other long-term assets on our Consolidated Balance Sheets.