Balance Sheet Components

12 Months Ended

Dec. 31, 2021

Balance Sheet Related Disclosures [Abstract]

Inventories consist of the following (in thousands):


	December 31,
	2021		2020
Raw materials	$	123,234	$	76,404
Work in progress	51,706		31,393
Finished goods	55,290		31,440
Total inventories	$	230,230	$	139,237

Prepaid expenses and other current assets consist of the following (in thousands):


	December 31,
	2021		2020
Prepaid expenses	$	70,218	$	30,069
Other current assets	125,087		61,685
Total prepaid expenses and other current assets	$	195,305	$	91,754

Property, plant and equipment consist of the following (in thousands):


		December 31,
	Generally Used Estimated Useful Life	2021		2020
Clinical and manufacturing equipment	Up to 10 years	$	452,876	$	372,077
Building	20 years	310,344		244,166
Leasehold improvements	Lease term 1	61,289		63,541
Computer software and hardware	3 years	117,986		108,068
Land	—	58,869		34,598
Furniture, fixtures and other	2-5 years	71,977		50,031
Construction in progress	—	367,686		163,492
Total		1,441,027		1,035,973
Less: Accumulated depreciation and impairment charges		(359,101)		(301,252)
Total property, plant and equipment, net		$	1,081,926	$	734,721

1 Shorter of the remaining lease term or the estimated useful lives of the assets

Depreciation was $92.1 million, $80.1 million and $73.1 million for the year ended December 31, 2021, 2020 and 2019, respectively.

Accrued liabilities consist of the following (in thousands):


	December 31,
	2021		2020
Accrued payroll and benefits	$	288,355	$	170,106
Accrued expenses	67,169		42,536
Accrued property, plant and equipment	46,561		27,692
Accrued sales and marketing expenses	41,387		34,488
Accrued professional fees	31,457		20,617
Accrued income taxes	33,838		30,130
Current operating lease liabilities	22,719		21,735
Other accrued liabilities	75,829		58,278
Total accrued liabilities	$	607,315	$	405,582

Accrued warranty as of December 31, 2021 and 2020, which is included in the “Other accrued liabilities” category of the accrued liabilities table above, consists of the following activity (in thousands):


Accrued warranty as of December 31, 2019	$	11,205
Charged to cost of net revenues	12,581

Actual warranty expenditures	(11,171)
Accrued warranty as of December 31, 2020	12,615
Charged to cost of net revenues	18,213
Actual warranty expenditures	(14,659)
Accrued warranty as of December 31, 2021	$	16,169

Deferred revenues consist of the following (in thousands):


	December 31,
	2021		2020
Deferred revenues - current	$	1,152,870	$	777,887
Deferred revenues - long-term 1	136,684		62,551

1 Included in Other long-term liabilities within our Consolidated Balance Sheet

During the year ended December 31, 2021 and 2020, we recognized $3,952.6 million and $2,471.9 million of net revenues, respectively, of which $481.1 million and $341.9 million was included in the deferred revenues balance at December 31, 2020 and December 31, 2019, respectively.