Balance Sheet Components

Inventories

Inventories consist of the following (in thousands):



	September 30, 2018		December 31, 2017
Raw materials	$	23,395	$	12,721
Work in process	11,090		12,157
Finished goods	14,373		6,810
Total inventories	$	48,858	$	31,688

Other Assets

Other assets consist of the following (in thousands):



	September 30, 2018		December 31, 2017
Capitalized commissions	$	8,651	$	5,515
Equity securities	9,862		—
Security deposits	4,259		3,557
Loan receivable from equity investee	—		30,000
Other long-term assets	2,692		4,821
Total other assets	$	25,464	$	43,893

Accrued Liabilities

Accrued liabilities consist of the following (in thousands):



	September 30, 2018		December 31, 2017
Accrued payroll and benefits	$	102,109	$	103,004
Accrued expenses	36,110		27,318
Accrued fixed assets	17,765		11,362
Accrued warranty	8,026		5,929
Accrued professional fees	7,774		6,316
Accrued sales rebate	7,765		11,209
Accrued customer credits	7,618		5,373
Accrued sales tax and value added tax	6,734		5,503
Accrued sales return reserve ¹	5,876		1,364
Accrued income taxes	4,111		12,405
Other accrued liabilities	15,147		5,779
Total accrued liabilities	$	219,035	$	195,562

¹ December 31, 2017 balance has been reclassified from accounts receivable, net to reflect the adoption of ASU 2014-09 (Refer to Note 1 “Summary of Significant Accounting Policies” of the Notes to Condensed Consolidated Financial Statements for more information).

Warranty

We regularly review the balance for accrued warranty and update based on historical warranty trends. Actual warranty costs incurred have not materially differed from those accrued; however, future actual warranty costs could differ from the estimated amounts.

Warranty accrual as of September 30, 2018 and 2017 consists of the following activity (in thousands):



	Nine Months Ended September 30,
	2018			2017
Balance at beginning of period	$	5,929		$	3,841
Charged to cost of revenues	10,874			5,201
Actual warranty expenditures	(8,777		)	(3,987		)
Balance at end of period	$	8,026		$	5,055

Deferred Revenues

Deferred revenues consist of the following (in thousands):



	September 30, 2018		December 31, 2017
Deferred revenues - current	$	356,109	$	267,713
Deferred revenues - long-term ¹	11,739		4,588

¹ Included in other long-term liabilities within our Condensed Consolidated Balance Sheets

During the three months ended September 30, 2018 and September 30, 2017, we recognized $505.3 million and $385.3 million of revenue, respectively, of which $125.6 million and $74.0 million was included in the deferred revenues balance at December 31, 2017 and December 31, 2016, respectively.

During the nine months ended September 30, 2018 and September 30, 2017, we recognized $1.4 billion and $1.1 billion of revenue, respectively, of which $313.4 million and $186.8 million was included in the deferred revenues balance at December 31, 2017 and December 31, 2016, respectively.