Balance Sheet Components

Inventories

Inventories consist of the following (in thousands):



	June 30, 2018		December 31, 2017
Raw materials	$	22,976	$	12,721
Work in process	12,396		12,157
Finished goods	11,880		6,810
Total inventories	$	47,252	$	31,688

Other Assets

Other assets consist of the following (in thousands):



	June 30, 2018		December 31, 2017
Capitalized commissions	$	7,947	$	5,515
Equity securities	4,862		—
Security deposits	3,734		3,557
Loan receivable from equity investee	—		30,000
Other long-term assets	2,759		4,821
Total other assets	$	19,302	$	43,893

Accrued Liabilities

Accrued liabilities consist of the following (in thousands):



	June 30, 2018		December 31, 2017
Accrued payroll and benefits	$	87,697	$	103,004
Accrued expenses	36,776		27,318
Accrued fixed assets	12,889		11,362
Accrued customer credits	11,552		5,373
Accrued income taxes	7,764		12,405
Accrued warranty	7,286		5,929
Accrued professional fees	6,876		6,316
Accrued sales tax and value added tax	5,955		5,503
Accrued sales return reserve ¹	5,554		1,364
Accrued sales rebate	3,772		11,209
Other accrued liabilities	10,633		5,779
Total accrued liabilities	$	196,754	$	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 June 30, 2018 and 2017 consists of the following activity (in thousands):



	Six Months Ended June 30,
	2018			2017
Balance at beginning of period	$	5,929		$	3,841
Charged to cost of revenues	5,728			3,690
Actual warranty expenditures	(4,371		)	(2,503		)
Balance at end of period	$	7,286		$	5,028

Deferred Revenues

Deferred revenues consist of the following (in thousands):



	June 30, 2018		December 31, 2017
Deferred revenues - current	$	321,148	$	267,713
Deferred revenues - long-term ¹	7,625		4,588

¹ Included in other long-term liabilities on our Condensed Consolidated Balance Sheet.

During the three months ended June 30, 2018 and June 30, 2017, we recognized revenue of $490.3 million and $356.5 million, respectively, of which $102.0 million and $61.3 million were included in the deferred revenue balance at December 31, 2017 and December 31, 2016, respectively.

During the six months ended June 30, 2018 and June 30, 2017, we recognized revenue of $927.2 million and $666.8 million, respectively, of which $187.7 million and $112.8 million were included in the deferred revenues balance at December 31, 2017 and December 31, 2016, respectively.