2. Significant Balance Sheet Components

Accounts Receivable, Net —Accounts receivable, net at December 31, 2019 and 2018 consisted of the following (in thousands):


	December 31, 2019		December 31, 2018
Accounts receivable - billed	$	57,184	$	60,037
Accounts receivable - unbilled		2,043		1,382
Allowance for doubtful accounts		(412)		(425)
Accounts receivable, net	$	58,815	$	60,994

Prepaid Expenses and Other Current Assets and Other Assets

Prepaid expenses and other current assets at December 31, 2019 and 2018 included $6.3 million and $3.8 million of prepaid royalties, respectively. Other assets at December 31, 2019 and 2018 included $3.0 million and $3.4 million of prepaid royalties, respectively. The prepaid royalties were primarily associated with MobileIron Threat Defense.

Property and Equipment—Property and equipment at December 31, 2019 and 2018 consisted of the following (in thousands):


	As of December 31,
	2019		2018
Computers and appliances	$	13,300	$	13,517
Purchased software		4,235		4,711
Furniture and fixtures		1,745		1,695
Leasehold improvements		3,403		3,503
Total property and equipment		22,683		23,426
Accumulated depreciation and amortization		(17,879)		(16,380)
Total property and equipment—net	$	4,804	$	7,046

Accrued Expenses—Accrued expenses at December 31, 2019 and 2018 consisted of the following (in thousands):


	As of December 31,
	2019		2018
Accrued commissions	$	4,810	$	4,398
Accrued stock-settled bonus		6,875		9,355
Employee Stock Purchase Plan liability		2,187		1,923
Other accrued payroll-related expenses		2,839		3,630
Accrued royalties		2,386		3,596
Other accrued liabilities		5,695		4,445
Total accrued expenses	$	24,792	$	27,347